installation of a solar collector
TRANSCRIPT
1 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
2008
Lydia Pforte
University of Karlsruhe
Germany
Emilie Girard
Ecole des Mines de Nantes
France
Installation of a Solar Collector
2 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Table of Contents
1. Introduction .............................................................................................................................. 3
2. Solar Panel Adjustment ............................................................................................................. 5
2.1. Location of the Solar Panels ......................................................................................................... 5
2.2. Orientation and Tilt ...................................................................................................................... 7
3. The Solar Collector System ......................................................................................................... 8
3.1. System Sizing ................................................................................................................................ 8
3.2. The Solar collector ........................................................................................................................ 8
3.3. Frame Construction .................................................................................................................... 10
3.4. Installation of the solar collectors .............................................................................................. 14
4. The Hydraulic System of the solar installation ........................................................................... 18
4.2. Water tank and heat exchanger ................................................................................................. 19
4.3. The Check Valve ......................................................................................................................... 20
4.4. The Circulating pump ................................................................................................................. 20
4.5. The Differential Thermostat ....................................................................................................... 22
4.6. The Expansion tank .................................................................................................................... 23
4.7. The Circulation Pipes .................................................................................................................. 23
4.8. The Anti-freezing fluid ................................................................................................................ 23
5. Measurements ........................................................................................................................ 25
6. Financial Analysis .................................................................................................................... 37
7. Conclusion .............................................................................................................................. 39
8. Reference List ......................................................................................................................... 40
9. Annex I ....................................................................................................................................41
3 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
1. Introduction
The Straw Bale House
Figure 1: Straw Bales House with its solar installation
The house of interest was a Straw Bale construction, a building method that uses straw bales
as structural elements, insulation, or both. It is commonly used in natural building and has
advantages over some conventional building systems as it is cheaper and easy available. Another
advantage is its high insulation value.
In terms of electricity, the Straw Bale house possesses its own power centre. It produces its own
supply of electricity from a small windmill (2,2 kW) installed in the garden. Charger regulator, battery
storage and inverter supply 230V electricity. Consequently the house is not connected to the public
grid, it is auto sufficient.
Figure2: Batteries installation
Concerning the hot water and the heating, the Straw Bale house possesses a wood boiler.
Technically, 2/3 of this wood fire capacity is drained off as hot water.
4 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure3: Wood boiler Figure4: Tank installation
This boiler was connected to a 1000 Litre storage tank for hot water supply; hence the house
was already auto sufficient in terms of hot water supply before our solar panel installation. However,
in order to take advantage of the summer period, the decision to install solar collectors which would
run from April to October was made. Moreover, since heating of the house is not needed during
summer period, the main aim of those collectors is the supply of hot water.
The Folkecenter offered four solar panels for our installation, which we had to build up in the
backyard of the house. This report will describe the different tasks of our project, starting with the
choice in the solar collectors’ localization, tilt and orientation. Then it will deal with the construction
of the support and its installation followed by the main details about the hydraulic system. Finally an
analysis of the measurements of heat output and efficiency done during 2 extreme days in August is
included.
5 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
2. Solar Panel Adjustment
2.1. Location of the Solar Panels
The Location of the Solar Panels is an important aspect of planning. Hereby not just the
factor of shadowing should be considered, but also aesthetical problems of a solar collector of 8 m²
and the connectivity to existent pipes should be included. In our considerations we made 5
assumptions of possible positions (Figure 5). All 5 options are placed facing the South to receive the
maximum solar radiation.
• Position Number 1 was moved inwards so that there were no shadowing effects, neither by the
windmill nor by the bushes. It was still close to the pipes. However aesthetically it would have
looked disturbing.
• Position Number 2 is placed next to the windmill. It would have stand in front of a flower bed
so that the view of the occupant would not have be hindered. The small distance to the
connection pipes was also an advantage of this position. However, this location was not perfect
due to shadowing effects of the windmill.
• Position Number 3 was standing free in the North-West of the garden. There were no shadows
affecting the performance of the Solar Panels from the existent Windmill. However, it was
planned to construct smaller windmills along the Western pathway in the near future, so there
would have been shadowing effects. Other disadvantages are the far distance from existent
pipes and the visual hindrance for occupants.
• Option Number 4 stood in the South-West corner of the garden. Here the solar panels were
also harboured against shadowing. The aesthetical criteria could also have been achieved. The
only disadvantage was the large distance to the existent pipes which would have to be
extended if this location would have been chosen.
• Option Number 5 was situated in the lower part of the garden, separated through a small
pathway. An advantage was the free area with no shadowing obstacles. However it was not
considered to be appropriate due to the large distance to the pipes and the aesthetically
separated appearance.
Table 1: Summary of Advantages and Disadvantages for the different locations
Proposed
Panel Advantages Disadvantages
1 - Close to the pipes (~ 4m)
- no shadow - Aesthetically not very appealing
2 - Close to the pipes
- Aesthetically very good
- small Shadow effects from the
big windmill
3 - no shadow from the bigger windmill and
bush
- shadow from future small
windmills
- optic
4 - no shadow
- optically good
- far away from the pipe
5 - no shadow - far away from the pipe (10m)
- looks separated
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Lydia Pforte - Emilie Girard Folkecenter
Option 2:
Panel Location (Simulation)
3
12
4
5
.
. .
.
.
Figure 5: The different considerations of the location of the Solar Panel
7 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
After discussing all advantages and disadvantages of different locations of our Solar Collector, we
decided to build the Solar Panel on Position Number 2, according to the fact that the shadow effect
will have no major impact on the collector efficiency.
2.2. Orientation and Tilt
Choosing a proper angle and direction of a solar collector is a very important step, without which the
system will loose efficiency. When determine the direction of the solar collector the following
considerations should be included.
• In the Northern Hemisphere: The collector should face South
• In the Southern Hemisphere: The collector should face North
Figure 6: Direction and angle solar installation
Secondly, and with similar importance a proper angle to mount the solar collectors has to be
determined. Generally speaking the best angle should roughly be equal to the latitude of the
location. Denmark has a latitude of 56° North, therefore the collector should face South at 56°.
However, if the tilt is lower than the latitude, upper than standard performance can be achieved
during summer.
Table 2: Theoretical daily energy gain in Estonia (60°N) (in kWh.m².day-1)
Months 30° 45° 60°
April 3.95 3.95 3.74
May 4.96 4.84 4.46
June 5.40 5.20 4.74
July 5.08 4.92 4.50
August 4.28 4.23 3.96
September 2.94 3.02 2.93
This table clearly shows that for a tilt lower than the latitude, the energy gain is higher. The
values are taken from Estonia which has latitude close to the one in Denmark. Consequently, since
the objective of the solar collectors for the straw bale house was to receive the most possible
available energy for the period from April to September, a lower tilt than 56° seemed to be the best
option. From Annex I one can notice that in average the highest global irradiance for the period April-
September is obtained for a 46° tilt at 56°N. According to all those data, we decided to tilt our solar
collectors at 45°.
8 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
3. The Solar Collector System
3.1. System Sizing
For our study we assumed that the Straw Bale House was constructed for a 4-person family
composed of 2 adults and 2 children. According to Esbensen Consulting Engineers the domestic hot
water consumption in Denmark is around 40L/person per day. Hence the domestic hot water supply
for the Straw Bale house would be around 160L/day. This value matches with the data for a large
family in the following Table 3. According to this table, the house would have needed about 6m² of
solar collector to supply all the domestic hot water (DHW) and 250L storage. On the other hand, in
northern United States, a rule of thumb for sizing collector allows 2m² of collector area for each of
the first two family members and 1.1 to 1.3 m² for each additional family member [1] . This leads to
6-7m² for the family. However, taking into account the fact that the hot water consumption is higher
in US (around 50L/person/day), it can be concluded that 6m² of solar collector should be enough to
supply DHW of the Straw Bale House [2].
Table 3: Solar System Sizing
Hot water consumption Solar collector Area Storage
Small Family 80 – 140 L 3 – 4 m² 140 – 230L
Large Family 140 – 200L 5 – 7 m² 230 – 300L
3.2. The Solar collector
The 4 solar panels were glazed Flat Plate Collectors. In other words, the collectors were
insulated and weatherproof boxes containing a dark absorber plate under a glass or plastic cover.
There are many types of flat plate collectors, which differ from one to the other by their tubing
arrangements (Figure 7). The type we used is represented on the figure, but consists of a metal black
plate which is filled with a fluid (either water or an antifreeze solution), hence it does not use pipes.
As the sunlight hits the dark absorber plate the black plate heats up and conducts this heat to the
fluid passing through the plate. The flat plate collector is by far the most common and the flooded
metal plate kind is known to be more efficient than the tube flat plate [3, 16].
Figure 7: Flat plate collector design Figure 8: Our flooded Flat Plate Collector
The efficiency of a solar collector is defined as the quotient of usable thermal energy versus received
solar energy. Besides thermal loss there is always optical loss as well.
9 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 9: Efficiency graph of solar collector performance
The heat loss is indicated by the thermal loss factor, given in Watt/m² collector surface and
the particular temperature difference (in °C) between the collector and the ambient air. The smaller
the temperature difference, the less heat is lost. Above a specific temperature difference, the
amount of heat loss equals the energy yield of the collector, so that no energy at all is delivered to
the solar circulation system. As a conclusion, a good collector has a high conversion factor and low
thermal loss. According to the typical Danish Weather, the heat loss should not be very high for our
installation. Some typical values for these factors are shown in Table 3.
Table 3: The different factors concerning different types of Collectors [4]
Type of Collector Conversion Factor Thermal Loss Factor
(W/m²°C)
Temperature Range
(°C)
Absorber (uncovered) 0,82 to 0,97 10 to 30 up to 40
Flat-plate collector 0,66 to 0,83 2,9 to 5,3 20 to 80
Evacuated-plate
collector 0,81 to 0,83 2,6 to 4,3 20 to 120
Evacuated-tube
collector 0,62 to 0,84 0,7 to 2,0 50 to 120
Figure 10: Percentage of monthly solar coverage (Annual Value: 65%)
Generally it is said that a properly dimensioned system can cover 50 to 65% of the yearly hot water
demand. In most cases in summer even the entire demand for hot water could be provided by the
solar heating system. Then the conventional heating system can be shut off completely. This is
particularly advantageous due to the fact that in this time period the heating system would work
with a low rate of capacity utilization due to the lack of heating demand. Thus, there is a larger
conformity between DHW demand and the solar energy supply than with the utilization for heating.
The objective of our system is therefore to supply all the hot water of the house during the summer
10 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
months as well as to supply a part of the energy for the heating of the house in parallel with the
boiler. The measurements were meant to give an idea of the efficiency of the installation and gave
the percentage of hot water which can be produced.
3.3. Frame Construction
A frame should stabilize and adjust the solar collector. Therefore planning the frame is one
very important part of the installation of the solar panel. The material we used was made of
galvanized iron-steel. The galvanization prevents the frame from rusting. We had to cut and drill all
the pieces in order to connect them together and to the ground. Therefore we also used a galvanized
paint to protect those parts, where the galvanization had been damaged. We had two possibilities
for the design of the frame. The first one was an isosceles one, similar to the installation for the solar
collector presented at the Folkecenter area (Figure 11). However, as we used only recycled materials
and our concrete blocks were not large enough we decided to build a perpendicular support with
feet (Figure 12).
Figure 11: Picture of a solar frame at Folkecenter.
To find out the size of all pieces of the frame, we had to use the Pythagoras theorem. Considering the
length of the panel (2.1m) and the fact that we wanted a 45° tilt for the panel, the height was given
by the classical trigonometric formula:
AB = AC x cos 45° (1)
2.1m 45°
C B
A
1.48m
0.15m
1.63m
Figure 12: The values for our
perpendicular support.
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Lydia Pforte - Emilie Girard Folkecenter
The result of the calculation amounted AB = 1.48m. However, taking into consideration that our
panels had water inlet fittings at the bottom, we needed to raise the height of the bottom of the
solar collector up to 15 cm from the ground, which gave a final length for the 4 top feet of 1.63m and
0.15m for the 4 bottom feet.
Figure 13: The values for each of the 4 solar collectors and the total area needed.
We decided to do one support for the total of all four panels, which gave us a total length for the
frame of 4.15 meters. This value takes in account a 1cm space between all the collectors. This small
space has been chosen to prevent any frictions due to material expansion. Finally we ended up to a
simple design, shown on the figure below.
Figure 14: Initial design
of the frame
1.03m 0.01m
2.1m
4.15 m
12 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
This structure has been evaluated to be strong enough to support the total weight of our
four solar collectors, admitting that one solar panel weighs around 50kg. However, a protection for
the panels from being lifted by the strong winds occurring in this area was missing. Hence, we
decided to add 8 metal angles on the bottom of the support and 2 on each side to maintain the
structure of the panels on the frame. The way the solar collectors were attached to the structure is
illustrated in Figure 16 (right site) as well as the connection of the frame to the concrete block (left
site). This figure also shows that two even pieces of iron-steel have been added between the inside
and outside feet of the top. Their role is to reduce the degree of freedom of the structure, to conduct
the pressure to other points and to make the frame more stable.
All the cuts and drills of the pieces were made in the workshop following our calculation. However,
when it was time to join all the pieces together on the site, the two lines of concrete blocks were not
exactly on the same level. Consequently the feet at the bottom were too short to be linked to the
structure. We finally had to cut four new feet of 35cm length instead of 15cm.
Figure 15: Final dimension of the frame
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Lydia Pforte - Emilie Girard Folkecenter
Figure 16: Details of the frame
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Lydia Pforte - Emilie Girard Folkecenter
3.4. Installation of the solar collectors
After finding the right place for the Solar Panel in the garden and building up the frame, the
construction work was started. At first old plans about the location of the existent hot and cold water
tubes were studied. These tubes with a diameter of 26 mm were previously used for water transport.
The tubes had to be removed in a 3 m long line from the windmill to the place on the solar panel
(Figure 17). Also a trench for the Temperature Sensor had to be dug from the Differential Thermostat
in the house to the Solar Panel. The trench was about 30 cm deep and 20 cm thick. The tube with the
sensor wire was laid on a 5 cm thick layer of sand. It was then covered with another 10 cm of sand
and a safety belt warning of the high voltage (Figure 17). Eventually the trench was closed.
Figure 17: The Installation of the Controller Wire and the Supply Tubes
For the fundament of the frame 6 concrete blocks were required. The concrete blocks were
about 110 cm long, 30 cm wide and 20 cm deep. At first the fundament was excavated with a
distance between the individual excavations in one line of 30 cm and between the front and the back
of 1, 40 m. The concrete blocks were placed and corrected to be immersed in water and exact
direction. An important detail was to base the concrete blocks about 5-10 cm above the ground level
so that the iron-frame is not exposed to standing water, accelerating the corrosion (Figure 18).
After the fundaments were placed accurately and closed, boreholes were drilled into the
concrete block of a diameter of 16 mm. These boreholes were used to fit in expansion bolts. The
expansions bolts had a diameter of 10 mm and a length of 100 mm, whereby the enclosed part was
30 mm long. These bolts have the characteristic that they expand when enforced into the concrete
and therefore are stable to hold the frame. They can also be used to adjust the frame; however, this
was not necessary for our frame (Figure 19).
Figure 18: The construction of the concrete fundament
15 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 19: Drilling the boreholes and constructing the frame
As seen in Figure 19 the primed pieces of the frame were then built on the expansion bolts.
First the basement was installed, followed by the feet and the connecting parts. The bolts used were
10 mm hexagon bolts with a length of 5 cm and 10 mm countersink screws with 2 cm length. About
50 bolts were used, the same amount as nuts; washers were just used for the hexagon bolts.
After finishing the frame, the 4 solar panels were mounted. Important hereby was to leave
1cm space for the expansion of the solar material at high temperatures. The Solar Panels have a rail
on the upper backside. This rail was fitted to the frame. To prevent the panels to be lifted at strong
winds, angles were attached at the bottom and fixed on the frame with screws (Figure 20).
Figure 20: The mounted Solar Collectors
In case of any exigency to remove the panels the following instruction should be abided. Due to the
fact that we had to screw the protection angle on the iron frame, we used countersink screws which
were than overlapped by the solar panels (Figure 21). When the angels have to be removed than the
Solar panel has to be lifted and a piece of wood has to be slid into the hollow space. Then the Solar
panel can be released and the screwdriver can counter the removal of the nut.
Figure 21: The approach to remove the
protection angels. A piece of wood has to be
placed between angle and frame
and then the screw can be removed.
16 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
The next step of the Installation was to connect the individual solar collectors with the tube
leading to the house. Therefore copper tubes were chosen as this material tolerates high
temperatures above 100°C. The connection coming out of the Flat plate collector was an 18 mm tap.
The 4 Solar Collectors were connected in parallel, each having its own “cold-water”-connection, so
that the risk of overheating was diminished. As seen in Figure 22 does the water inlet on the bottom
of the Solar Panel go into the Panel, gets there heated and reunites on the top, where it is led into
the water outlet.
Figure 22: The connection of the copper tubes.
The Water Inlet was not connected to the Solar panel taps on the right side directly, but was
led through a 4 m long copper tube to the other side where it was fed in. The reason for this type of
flow conditions is that if it would have been fed into the solar panels directly, the colder water would
have gone the easiest way through the first panel on the right hand side. The water would not be
going through the 3 other solar panels and therefore not heated adequate. With our kind of system,
the waters easiest way to go on the bottom is the left panel. However, on the top this way is the
catchiest as there are water jets coming from the other panels hindering the unhampered passage.
For the water jet going through the right panel the bottom way is the most hampered one, while the
way on the top is the easiest.
The copper tubes were connected with five 1/2 Inch T-Fittings, one Elbow and 2 Reducer, reducing
the diameter of the plastic tube (26mm) to the diameter of the copper tubes (18mm)
In case one has to buy new Reducers for the Plastic Tube, a 26 mm wide tube is very rare today; in the
area it is only available in Bedsted.
Due to the negative effect of air in the system (artificial high pressure, limited heat conduction)
an additional Air Release Valve was installed to release the air produced in the beginning phase when
water is added to the system and when temperatures get so high that the water is evaporated. On
17 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
the bottom a water outlet valve was also installed so that in case of a necessity to empty the solar
collector, the water can be released easily. On the top the body with the attached sensor was also
installed and connected to the wire leading to the controller in the house (Figure 22).
After all fittings were connected several test runs were done. Leaking fittings were repaired or
screwed up.
18 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
4. The Hydraulic System of the solar installation
There are actually two ways of using the sun power to heat water. One is called Passive solar
heating. Passive solar refers to the usage of sunlight for energy without active mechanical systems.
The second solution, Active solar heating, requires a pump to run the anti-freezing product through
the circuit. It needs additional components which make it more complicated but also give more
control over the system. In the Straw Bale House the Active Solar Solution was chosen. Additionally
there are two basic designs used in an active solar heating system: Open Loop and Closed Loop
systems. Open loop systems heat and circulate household (potable) water directly in the collectors
before it is distributed in the household. Closed loop systems use a heat-transfer fluid to collect heat
and a heat exchanger to transfer the heat to household water. This fluid is usually a glycol-water
mixture raising the freezing temperature and therefore making closed-loop systems effective in areas
with freezing weather. For this reason, closed loop systems are preferred in Denmark.
4.1. The Straw Bale House’s hydraulic system
The active closed loop circulates the anti-freezing product through the solar collectors to a
heat exchanger which transfers the heat to the water storage tank. This system uses a small
Circulating pump activated by a differential thermostat controller that senses when heat is available
in the solar collectors. Technically, this sensor sets off the pump when the temperature in the solar
collector is hotter than in the water tank.
Figure 23 below shows the usual way to link all parts together. The Circulating Pump is hereby
located at the “cold” pipe. However, for the Straw Bale House, where the tank and the expansion kit
were already installed, we had some place issues to install the pump at the “cold” pipe. Therefore, it
has been added on the “hot” pipe, which should not create any problems since it can works until
110°C. The only problem caused is that the pump is heated additionally by the hot pipe rather than
being cooled by the cold pipe. This will probably shorten its lifetime.
Figure 23: General Scheme of a solar heating system
19 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
4.2. Water tank and heat exchanger
As can be seen in Figure 25 a heat exchanger should be existent in a tank. Its function is to
transfer the heat from the Antifreeze liquid passing through the Heat exchanger to the tank water.
The volume of the tank should be about 1.5 – 2 times greater than the daily water consumption. As
the water consumption in the Straw Bale house amounts 160 L/day, the tank should have a volume
of about 230 L for the warm water storage [5]. Because the heating system should also be delivered
with hot water from the tank and as the house is completely self-sufficient, we decided to install a
bigger tank with a storage capacity of 1000 L. It is a Solus II from Consolar, a German producer. The
table below gives important technical data.
Table 4: Technical data for the storage tank [6]
Technical Data - SOLUS II 1000
Storage capacity [V] 1000 L
Empty weight [m] 225 kg
Diameter without isolation [D] 85 cm
Diameter with isolation [D] 111 cm
Height with isolation [H] 206 cm
Isolation Cover: 15 cm
Sides: 10 cm +2.5 cm
Max storage temperature [T] 90°C
Collector area [A] 8 – 16 m²
The tank has a tall cylindrical form to develop temperature
stratification. This allows an optimal usage of the heated
water in the upper area without heating the complete
content.
Solus tanks are also characterized by the special layer
system whereby the specific flow conditions of the warm
water allow 2- 3 times more water to be heated. Another
advantage of Solus storage systems is the low volume of
the heat exchanger, which amounts 3 – 15 L [7]. Hence the
warm water is heated very fast in the flow path and
therefore more hygienic even when the water stays longer
in the tank (Figure 25).
Figure 24: The existent hot water
tank, a Consolar Solus II . [6]
20 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 25: The assembly of the Solus tank [7]
4.3. The Check Valve
A check valve permits the fluid to flow in one direction only. It prevents heat loss at night by
convective flow from the warm storage tank to the cool collectors through the Return. Check valves
may be of the "swing" type or the "spring" type. At our installation a check valve was already existent
in the pipes provided in the house.
4.4. The Circulating pump
In order to pump the solar collector liquid from the solar collector through the heat
exchanger into the storage tank and back again, a small circulation pump has to be used when the
storage tank cannot be placed higher than the solar collector. In the Straw Bale House, this pump
was placed on the “hot” pipe because of place issue. But it is usual to install it on the “cold” pipe to
prevent it from high temperatures during operation. Eventually, stop valves were mounted in front
of and behind the pump so that the entire system did not have to be emptied when replacing a
defective pump.
The circulating pump is, with the controller, the only component which needed to be powered by
electricity. Therefore a high energy efficiency pump was the best option to consume as less
electricity as possible. The choice of the pump also took into account the flow of water which had to
go through it and the head of the highest point of the system. The prevalent flow rate in small solar
heating systems amounts 30 to 50 L/h*m² of the collector surface [5]. Considering the 8 m² of solar
21 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
collector surface, a flow between 0.25 and 0.4 m³/h was required for a maximum height of 2m.
According Figure 26, the model ALPHA2 from the brand GRUNDFOS is the model needed.
Figure 26 : Pump Types for a given flow and head [8]
a)
b)
c)
d)
Figure 27: Data about the Pump Grundfos Alpha 2 25 – 40. a) A picture of the pump b) An explanation what the
different data mean c) the energy category is A, the best category one can achieve in Europe d) Several details
about the pump with the max Flow, the Head, the temperature it can be used for and the operation pressure.
Thus the circulating pump we decided to install was a GRUNFOS ALPHA2 25- 40.It is an energy label
A, which indicates that the energy-saving level of the pump is the highest possible. The advantage of
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this pump is that it will reduce the power consumption considerably, reduce noise from thermostatic
valves and similar fittings and improve the control of the system.
From the GRUNDFOS company, the price of this device is 323€ - which is around 2,410 DKK (phone
call). Therefore we decided to buy it on a discount website for only 177.5€ or 1,324.27 DKK. [9]
Finally, this pump has been declared by the Folkecenter to be too efficient
and too expensive for working only on day time and only during the summer.
Therefore another pump was bought for the Straw Bales House. This pump
was an UPS 25-40. It is not an “Energy Label A” pump; consequently, it was
decided to run the pump at the first speed in order to consume the least
electricity possible. Indeed there are three speeds, which consume 30W,
45W and 60W respectively. This pump did cost 750DKK (100€) VAT, which is
600DKK (80€) pre-tax [10].
Figure 28: The final
pump
4.5. The Differential Thermostat
The Differential Thermostat, or controller, is one of the most important devices of a solar
heating system. Its main function is to regulate the functioning of the pump. When the fluid in the
solar panels is not heated sufficient, the warmer water in the tank will be replaced by cooler water
from the solar collectors as long as the transfer fluid pump works. In order to guard against this loss,
the pump has to be switched off. Likewise it has to be switched on when the temperature in the solar
collectors rises higher than that of the tank. Usually the temperature of the collector should be 5 –
8°C higher than the tank temperature until the controller sets up to start the pump. When this
temperature difference sinks to 2 - 3°C, then the controller should shut off the pump [11].
A temperature difference of 6°C has been chosen to start the pump of our system and 4°C to turn it
off.
This kind of controller we installed switches off/on the pump automatically when a certain
temperature in the tank and solar collectors is passed. There are also simpler forms of controlling the
pump, whereby the pump is started and stopped by a time switch or in accordance with light
intensity. However, those methods of control are less efficient, that’s why we decided to use the
Differential thermostat.
Figure 29: The differential
thermostat Resol Deltasol BS [6]
For our project we decided to include the
differential thermostat Resol DeltaSol BS/3 (Figure
29). This controller has two standard-relays and
one additional thermostat function. The limitation
of the tank temperature amounts 20°C to 95°C.
The power supply amounts 115V, the power
consumptions 2 VA.
We ordered the Controller at Varmt vand fra
solen in Denmark, the prize amounted 1,390DKK-
which is about €186- [12].
23 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
4.6. The Expansion tank
The liquid in the solar collector as any liquid expands when heated up. Therefore, to prevent
overpressure in the system an expansion tank is necessary. In the Straw Bale House, the pressure
expansion tank was placed on the “hot” pipe where overpressure can occur. The operating pressure
of the solar heating systems, which is controlled by a nanometer, was set down to 1bar. The safety
valve, on the top of expansion tank should open at approximately 0.3 bar triggering pressure. The
expansion tank keeps the pressure in the system stable and takes up the amount of exceeded heat-
transfer fluid that is caused by a temperature difference. For safety reasons, the volume of the
expansion tank has to be sufficiently large. It should be able to take up the entire volume of heat-
transfer fluid. An expansion tank of 25L capacity was already installed in the Straw Bale House.
4.7. The Circulation Pipes
Within the solar heat circulation, heat is transported from the collector to the hot water
storage tank. In order to minimize heat loss, the distance from the collector to the tank should be as
short as possible.
For systems in family homes, copper pipes with a circumference of 15 mm to 18 mm are enough to
guarantee an optimal transportation of heat. In our system copper pipes of 18 mm diameter were
used [5]. The fitting for the copper pipes were ½ Inches. Finally pipes were sufficiently insulated with
a 30 mm – polyurethane foam pipe. The insulation had to be able to withstand high temperatures
and the outdoor section had to be UV and weather-resistant.
Figure 30: The polyurethane foam
pipes used for insulation
4.8. The Anti-freezing fluid
The collector loop circulates an antifreeze solution. The used Propylene glycol is hereby the
most common heat transfer fluid. It is a non-toxic substance and more commonly used as food
additive, although it is not considered to be a potable fluid. Propylene glycol was mixed with 60 %
water. Inhibitors may be added to increase the lifetime of the fluid, which breaks down over time
due to overheating, creating a sludgy deposit that can clog the collector loop, as well as reduce the
solution's effectiveness as an antifreeze. This inhibitor has not been used in our case since the anti-
freezing solution is changed frequently.
24 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 31: Scheme of the installation in the Straw Bale House
25 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
5. Measurements
The straw bale house is occupied by 4 persons, 2 adults and 2 children. Together with the
electricity produced by the two windmills it demonstrates a decentralised solution for producing
heat and electricity by ones own. But how much heated water will be produced? And when will be
the Payback time? In our 2nd part of the report we tried to answer these questions. The values that
were measured are shown in table 5.
Table 5: Measurements done for the straw bale house
Value Unit Explanation
Irradiance W/m²
To receive not only an average value, but to have a specific value
for a specific day in this area, the Irradiance was measured every
5 min with a Hand Pyranometer 98 HP
Temperature
Collector °C
The temperature of the water at the hottest point of the Solar
Collector was measured with a temperature sensor
Temperature hot
part of the Tank
(Sensor 1)
°C By measuring the temperature on the tube leading to the tap,
we can say what the hottest point of the tank
Temperature cold
point of the Tank
(Sensor 2)
°C The temperature of the return water (outlet), which is almost
similar to the cold bottom water of the tank.
Air temperature °C The temperature of the air is important to calculate the
efficiency, it was measured with a thermometer
Energy flow kWh To know how much Energy was produced in one day, the power
was measured with a Picocal Heat Meter
Water flow l/h The flow of water through the system was also measured with
the heat meter
Volume m³
Temperature Inlet
Tank °C
The temperature was here measured before entering the tank.
Hence the heat loss of the tubes between collector and house
could be measured.
The different positions of the sensors are shown in figure 32.
26 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
H ot w ater from collector
R eturn
Position of Sensor 1 from 13/08/08
Initial Position of Sensor 1
Position of Outlet Sensor of H eat Meter
Position of In le t Sensor of H eat Meter (Sensor 2)
Tube going to show er
Position of In let Sensor of Heat Meter
Position of Outlet Sensor of Heat Meter (Sensor 2)
Initia l Position of Sensor 1
Position of Sensor 1 from 13/08/08
Tube going to shower
Return
Hot water from collector
Figure 32: The tank, tubes and different sensors which were used.
To understand the dependence of the production of hot water and the irradiance we did some
measurements on different days with different weather condition. However in this report we only
included the results of our last two measurements on the 13/08/08, a cloudy day and on the
15/08/08, a sunny day. The measuring times were from 9:10 am till 5:10 pm with a 5 minute
frequency for the Irradiance and a 10 minute frequency for all other values. Unfortunately the
measurement cannot be 100% correct, as the temperature of the tank cannot be measured directly.
The tank temperature is calculated through taking the average of the hot part of the tank (Sensor 1)
and the cold part of the tank (Sensor 2). As the temperature is stratified in the tank, the average of
these two extreme values will give the most reliable actual tank temperature.
Sensor 1 was hereby placed at the top tube coming out of the tank and going to the tap. Therefore
we used the sensor as a contact sensor touching the copper tube and isolated it with mineral wool
against external impacts. As copper is a very good heat conductor, good results were expected.
Sensor 2 was placed at the cold return from the tank to the solar collector. This also led to an error as
the temperature of the Return is the temperature of the glycol, which is decreasing when the pump
stops as it gives all its heat to the tank. The actual tank temperature at the bottom however, is
increasing as it receives heat from the heat exchanger and therefore also from the return.
The methodology of linking one sensor to the tank water temperature (Sensor 1) and one sensor to
the circulating system temperature (Sensor 2) presents a disadvantageous situation as of course tank
water and the glycol of the collector system behave unequal to some conditions. However, we
decided that this was the most precise form of taking temperature measurements.
As the 13th
of August was a very cloudy and rain-laden day, we did not expect to obtain increased
results, above all not from the tank temperature. However the temperature ought to stay constant.
27 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 33: The Irradiance for the 13/08/08, a day with many extremes.
As shown in Figure 33 did the Irradiance fluctuate very strong reaching maximum values of
1440W/m² at 2:30 pm and minimum values of 50 W/m² at 9:40 am. The average value for the 13th
August was 311.9 W/m².
The air temperature amounted between 14 and 19 °C with the Maximum at 11:05 am and the
Minimum at 12:55 am (Figure 34). The strong fluctuations were due to fast weather condition
changes between storm and clouds. The average air temperature amounted 16.3°C.
Figure 33: The highly fluctuating air temperature.
For the collector system we measured 4 different values with the temperature of the hot part of the
tank (Sensor 1), the temperature of the collector, the temperature of the Inlet and the Outlet of the
tank (Sensor 2).
28 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 34: The different temperatures of the system
In Figure 34 one can see the difference between the sensors showing the temperature of the
Collector system (Collector, Inlet and Outlet), which are more controlled by Irradiance and Air
temperature and the sensor showing the hot part of the tank temperature (red line) and the overall
tank temperature (brown line). The collector temperature of the highest Irradiance (1440 W/m²)
amounted 58.8 °C for this day and the temperature for the lowest irradiance (50 W/m²) amounted
28.3 °C. Through the whole day the temperature rise of the collector amounted 12.4 °C. As the water
of the Outlet (and the Inlet) stagnates during the night (no pump running), the temperature in the
morning equals the actual bottom tank temperature. As one can see the overall tank temperature in
the morning amounted 29°C, whereby the hot part of the tank amounted 39°C and the cold part
amounted 19°C. The temperature of the tank increased at this day about 3°C from 28.9°C in the
morning to 32 °C. However, the temperature of the hot part in the tank decreased at 1°C through the
day. The heat of the 3 kWh produced was stored in the lower part of the tank. This was due to the
fact that there was almost no pump activity at this day. Therefore only Diffusion occurred rather than
Convection.
Uncertainties do exist for the sudden increase of tank temperature at 10:55 am. This error does not
occur due to human failure by forgetting to look if the pump is running. The flow in the system which
was also measured showed only 0 L/h until 11:20 am what means that the pump was not running.
Another explanation could be, that due to fact that the pump was not running, but the collector was
heated up to 50°C at this time convection occurred, conducting heat through the system.
The difference between the Collector temperature and the temperature of the Inlet tank makes clear
that there are still high heat losses in the hot water tubes. This could be due to some tubes, which
were still not well isolated.
29 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 35: Aside from the morning, the values agree well with the features of a turned off pump
Figure 35 shows how the values behaved with the heat transfer through pumping. Even if it was not a
perfect day to show how the hot part of the tank (red line) became hotter during pumping heated
water through the heat exchanger. Particularly after 11:10 am the energy could be saved during
pumping stops with a small decrease due to heat loss. However, the first period of the day is an
outlier from the concordant values of the rest of the day. Here the temperature is decreasing rapidly.
One reason could be that there was just a residual of hot water in the top layer of the tank which was
than used by turning the tap on. The tap was turned on during every measuring period to obtain the
actual tank water and not the stagnating water in the tube. After flushing this hot layer the average
water in the tank emerged. This could also be the reason why the cold and the hot part of the tank
are concordant between 11:05 and 11:25 am. One can also see that the cold water temperature of
the tank is also decreasing during the stops of the pump. The stagnating water of the heat exchanger
conducts more heat to the tank, cooling itself even more during pumping breaks. After the pump
switched on an increase in temperature can be seen because new, less cold water is injected. The
reason for the fluctuating values even when the pump is running is due to fluctuating collector
temperatures which transfer this fluctuation to the Outlet. Hence it is important to know that the
actual cold temperature part of the tank water would not underlie such fluctuations. It is more likely
that it would behave like the hot part of the tank and conduct the obtained heat to the upper layers
of the tank. The actual tank temperature of the cold part can in this figure seen in the first part until
10:40 am, where the pump has not worked jet and hence the temperature of the Outlet is equal to
the tank temperature. Similarly does the curve behave in the last part after 4:15 pm, where the
30 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
pump has not worked for a while and therefore the temperature of the Outlet becomes similar to
the temperature of the storage tank.
To obtain the energy produced on the 13th we used besides the measuring of the heat meter a
formula to calculate the energy output Q.
Q = m * Cwater * ∆T (2)
Whereby m is the mass, Cwater is the specific heat capacity of water and ∆T the tank temperature
difference between the start and the end of our measurement.
Table 6: The values concerning the energy output for the 13/08/08
13.08.08
Energy delivered to
the tank
3 KWH
10 800 KJ
Top Temp
(°C)
Bottom
Temp (°C) Mean Temp (°C)
AM 39 19 29
PM 38 26 32
As the specific heat capacity for water is 4200 kJ/kg°C and the mass for our water to be heated
amounted 1000 kg, the energy output Q for the 13/08/08 was 3.5 kWh.
(Q= 1000 * 4200 * (32-29)
Q= 12 600 000 Joules = 3.5 KWH)
This value of 3.5 KWH coincides with the value given by the flow meter. It means that 3KWh are
needed to increase the 1000 L of water at 3°C.
However, as the hot part of the tank is not heated for this day (see Figure 36), there cannot be an
overall increase in tank temperature. To calculate the actual amount heated, we took the same
formula converting it to m.
m= �
������ ∆ (3)
Taking 3 kW for Q and only the bottom part of the tank, which was heated (∆T =26 – 19), the actual
mass heated was 429 kg. This calculation shows that all the energy delivered to the tank (3 KWH) has
been used to warm only half of it (430 Liters) from 19°C to 26°C, and not used to warm all the
capacity of the tank.
The efficiency of the tank can be calculated with the formula
η = ���� �
���������� ������� �������� (4)
Using the energy of 3 kWh and the average Irradiance of 312 W/m² our efficiency for this day is
about 15%.
31 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
The 15th
of August was the completely opposite to 13/08/08. This day was very sunny with an
average Irradiance of 916.91 W/m². The Maximum Irradiance was 1278 W/m² at 10:35 am and the
Minimum Irradiance was 221 W/m² at 9:30 am (Figure 36).
Figure 36: The overall relatively high Irradiance of the 15
th of August.
As well as the Irradiance behaved the air temperature. The temperature increased from 17°C in the
morning up to 21°C in the afternoon. The average air temperature of this day amounted 21.9°C
which is several degrees higher than the 16.3°C of the 13th (Figure 37).
32 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 37: The stepwise increase of the air temperature.
The temperatures we measured at the collector, the inlet and the tank show a good consistency with
a sunny day. The collector temperature increased through the day from 35.6 °C to 59 °C in the
evening. However the highest collector temperature was reached at 1:50 pm with a value of 66.3 °C.
Looking at the collector temperature (blue line) in figure 38 a good consistency with the location of
Sun can be observed. Following this line, the highest point of Sun at about 1:30 pm led to the highest
temperature in the collector; after this point the sun moved forwards, pointing the collector not in a
perfect angle anymore and therefore leading to a decline in temperature. The Inlet temperature was
still 1°C smaller, thus showing a loss of heat on the way from the collector to the house.
The temperature of the tank was also showing good consistency to a sunny day condition. As the
heat is here added, the temperature in the tank should rise constantly. What was unclear was the
fact that in the first part of measurements the temperature of the outlet was higher than the
temperature of the hot part of the tank. This could have been due to incorrect reading of the hot
temperature at Sensor 1. The lowest tank temperature was reached at 9:30 am, where it amounted
32°C; the temperature increased till 50°C at 5:10 pm and probably increased further after the end of
our measurement. So the attained temperature over 7 hours 40 minutes for this day was 17.39°C.
That is about 6 times more than on the 13th of August.
33 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 38: The temperature rise during the day.
At 9:40 am there was a sudden temperature rise in the tank coherent with a temperature decrease in
the solar collector. Because the pump was not running until 9:40 am the tank temperatures
remained low whereas the collector was already heated during the sun. As one can see in figure 39
the pump started at 9:40 am and was followed by an increase in tank temperature, especially the
cold part. When the pump turned off for about 5 min at 9:50 one can see that the temperatures of
cold and hot part are decreasing as well and the collector temperature is increasing rapidly. After this
5 min when the pump turned on again, the collector temperature shows again a sudden decrease in
temperature (blue line, Figure 38). At this day the pump was running over the whole day. The
average flow, transported through the system was 155.13 L/h.
34 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
Figure 39: The Pump was working during almost the whole day on the 15
th of August.
On the 15th our energy output amounted according to the heat meter 20 kWh. To check this value
we included again the formula (2), adding the values delivered in table 2.
Table 7: The values important to calculate the energy output
15.08.08
Energy delivered to
the tank
20 KWH
72 000 KJ
Top
Temp (°C)
Bottom
Temp (°C)
Mean Temp (°C)
AM 34.5 28 31.25
PM 50 49 49.5
The energy output of this day amounted 21.3 kWh. As it can be seen from the table both top and
bottom temperatures in the tank reached 50°C. In other words, 20 KWh is the amount of energy
capable to warm 1000L from 30°C to 50°C.
As 1000 L of water can be warmed at 3°C using 3KWh of energy (13/08/08) or warmed at 20°C using
20KWh of energy, we concluded that 1KWh is required to rise temperature at 1°C.
It is clear that the family could only take hot water from the obtained values of the 15th. To know
how long the family could live from this heated water we included the following calculations of the
consumption.
Hereby we had to assume that no new heat is added on the following day and that 4 people
consume in average 160 L with the hot tap at 45°C and the cold tap at 15°C. To know now how much
L we use from the storage (T=50°C) we include the following formula.
35 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
T tap= ��������� � ���������
����������� (5)
By using the following steps the amount of used tank water was calculated
45°C = ��°� ��!°��
�� and x+y = 160 L
45°C *160 L =15°C *(160L-y) +50°C y
7200 °C L= 2400°C L + 35°C y
y= 137 Liters
Hence when 160 Liters were used from the tap, only 137 Liters came from the 50°C hot tank.
Consequently, by the end of the day, 137 Liters of cold water (15°C) were added to the tank to
replace the hot water used. The tank therefore included 863 Liters of 50°C and 137 Liters of 15°C
warm water. After that the average temperature was calculated.
T average = "#$�!��$%��
�!!! = 45.2°C
The average temperature of the tank was 45.2°C. The calculation does not take in account the loss in
the tank over the night. However, our measurements have shown that there were no significant
losses.
Since the water in the tank is now 45.2°C, on the second day the hot water consumed at the tap
comes 100% directly from the tank. This means that by the end of the day 160 Liters of cold
freshwater will be added to the tank to replace the daily consumption.
Taverage = "&!&���#!��
�!!! =40.2°C
Hence on the end of the second day the tank temperature amounted 40.2°C.
Continuing this calculation on the third day we held the following water temperature in the tank.
T average = "&!&!��#!��
�!!! =31.2°C
These calculations show that after a sunny day, like Friday 15th of August, the energy delivered to
the tank is enough to supply the hot water consumption of the 4-people family during two days, if
the day after the sunny day is not profitable and does not deliver energy to the tank. This result
assumes that there is no heat loss during the night.
This outcome can be correlated with the European data about hot water consumption, which says
that the individual average energy consumption for hot water is about 950 kWh per year. At a daily
scale the consumption 2.6 kWh per day per person. Hence for our family approximately 10 kWh of
energy are needed per day and 20 kWh for two days [13].
The efficiency of the 15/08/08 was again calculated by including Irradiance, Energy produced, area of
the solar collectors and time.
36 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
η = ���� �
���������� ������� �������� (4)
By taking the values 20 kWh and 917 W/m² the efficiency for the 15th of August amounted 36%. At
the maximum values of Irradiance between 11:30 am and 12:30 am the efficiency even achieved
46%.
The 2 days of measurements clearly proved that the efficiency was directly linked to the Irradiance.
The conclusion was that the higher the irradiance is, the higher is the efficiency. However, it also
shows that even with a nice sunny day with a high average irradiance (900W/m²) the efficiency does
not exceed 40% in average. Nearly 50% efficiency can be achieved at noon when the position of the
solar collectors is the best according to the sun position.
37 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
6. Financial Analysis
As our measurements were not continued over a longer distance to offer more statistical
background, we decided to include average data for Ydby in our financial analysis. Considering the
average irradiance over the year in Skive (Figure 40), located not so far from Hurup Thy, a financial
analysis has been done to determine the payback time of the installation. These calculation has been
done, given a current oil price at 0.15€/kWh and an electricty price at 0.26€/kWh.
Figure 40: Monthly Irradiance in Skive [14]
Given an irradiance in Wh/m²/day, the energy produced by month has been calculated as following;
E = I * A * n * η (6)
Whereby E presents the produced Energy, I the Irradiance, A the collector area, n the number of days
per month and η the collector efficiency.
On the other hand the energy required to supply the family has been determined, according to a 2.6
kWh/day/pers energy consumption for hot water [15]. To calculate the overall family energy demand
following calculation established.
Efam = Eind * N* n (7)
Efam is hereby the Family energy demand, Eind the Individual energy demand, N the number of people
in a family and n the days per month.
In figure 41 the results for the produced energy and the energy demand are compared against each
other. One can see that the solar installation can supply the family from April to September
completely. The figure also shows that even supply more hot water can be supplied than needed by
the family during the summer period. In order to obtain the energy saving with such an installation,
only the energy demand which has been supplied by the solar collector was taken in account for the
calculation. This means that from April to September, when the solar panels supply all the demand
38 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
the energy saving would reach 1900 kWh. However, over the whole year the energy saving was
calculated from the energy produced from January to March and October to December added to the
1900 kWh energy saved during the 6 other months. This annual savings amounts 2600 kWh.
Figure 41: Average energy demand and produced energy with our solar installation
At a new acquisition the prize of our 4 solar panels would have been 40 000DKK, which is about 5 400
Euros. The current oil and electricity prices are rising and a stop in this development is not in sight.
The paybacktime was calculated by taking the actual oil price of 0.15 Euro/kWh and the actual
electrictiy price in Denmark of 0.23 Euro/kWh. Then, according to the current oil and electricity
prices and the cost of the solar collectors two types of pay back time were calculated. The first one
only considers the period the solar collcector will be in use, between April and September. The
second one is considering the whole year.
Table 8: Pay back time for different conditions.
Total energy supplied by the installation from April to Sept (kWh) 1903.2
Total energy supplied by the installation over the year (kWh) 2616.5
Price of oil : 0.15 Euro/kWh Money Saved (€/yr) PAY BACK TIME (years)
April to September 285.5 18.9
whole year 392.5 13.8
Price of electricity : 0.23 Euro/kWh Money Saved (€/yr) PAY BACK TIME (years)
April to September 437.7 12.3
whole year 601.8 9.0
Taking into consideration that the actual oil price is 0.15€/kWh, the payback time for our installation
would be 19 years if we only consider the 6months period from April to September, and nearly 14
years considering the whole year. Compared to electricty, which is actually more expensive than oil,
this payback time would be reduced to 12 and 9 years respectively. However, due to the actual
energy crisis, both oil and electricity prices are forcasted to increase in the next years, which means
39 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
that the payback time would be even more reduced. Eventually, assuming a 25 years life time for
such solar collectors, a solar installation in Hurup Thy is a not only an ecological commitment, but
also a good financial investment.
7. Conclusion
A lot of components of renewable energies argue that solar installments do not have a future in
colder countries with winter times and colder summers as Denmark is. However, this argument was
proved in our record to be wrong. Of course is a dependency on one particular energy system the
wrong way and of course can solar not deliver enough warm water during the whole year in a
country like Denmark. But with a mix of several energies like solar and wind, a balanced energy
production can be achieved. Also biomass is an important part of this backup-system as it is the only
renewable energy source with very long storage qualities. What people have to learn today is that
energy is a limited resource. For almost all Western Europeans it is seen as normal to receive energy
whenever they ask for. In the future this kind of wasting energy will not work any more, be it because
of remarkable expensive energy prices or the change of society to a more sustainable manner of
energy production. Living in a self-sustaining house means also that the inhabitants will have to live
with limited resources and limited capacity. Hence the sustainable acquaintance with our resources
is as important as to change to renewable energies.
40 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
8. Reference List
1. www.nrel.gov/docs/legosti/fy96/17459.pdf [Last visit: 12/08/08]
2. www.thermomax.com/consump.htm [Last visit: 12/08/08]
3. www.apricus.com/html/solar_typesofsolar.htm [Last visit: 11/08/08]
4. The Solarserver – The internet platform for solar energy:
www.solarserver.de/wissen/sonnenkollektoren-e.html#fla [Last visit: 13/08/08]
5. The Solarserver – The internet platform for solar energy:
www.solarserver.de/wissen/solaranlagen.html. [Last visit: 15/07/08]
6. Consolar – Solus II.: http://www.consolar.de/produkte/speicher/solus.html#c173
[Last visit: 15/07/08]
7. Solus II: www.consolar.co.uk/documents/Solus%20ll/SOLUS_TD_WEB.pdf [Last visit:
19/08/08]
8. http://www.grundfos.com/web/grfosweb.nsf/Webopslag/grundfos+alpha
9. Pumpendiscounter Germany: www.pumpendiscounter.de [Last visit: 24/07/08]
10. www.cgi.ebay.fr/Circulateur-chaffage-central-Grundfors-UPS-25-40-
130_W0QQitemZ22025836562QQihZ012QQcategoryZ92187QQcmdZViewItem [Last visit:
12/08/08]
11. http://www.solarserver.de/wissen/sonnenkollektoren-e.html#fla [Last view: 29/07/08]
12. Varmt Vand Fra Solen: http://www.varmtvandfrasolen.dk/ [Last View: 15/07/08]
13. http://ec.europa.eu/energy/atlas/html/hotdintro.html [Last View: 10/08/08]
14. http://re.jrc.ec.europa.eu/pvgis/apps/radmonth.php?lang=en&map=europe [Last view:
15/08/08]
15. http://ec.europa.eu/energy/atlas/html/hotdintro.html [Last visit: 10/08/08]
16. Twidell, J., Weir, T., 1986: Renewable Eenrgy Resources. E & FN SPON
17. www.gogreenheat.com /images/Resol%20BS%203.jpg [Last visit: 16/08/08]
18. http://www.builditsolar.com/References/SolRad/Lat56.htm [Last visit: 23/07/08]
19. http://www.engineering.com/SustainableEngineering/RenewableEnergyEngineering/
SolarEnergyEngineering/PassiveSolarSystemsSolarHotWater/tabid/3892/Default.aspx
[Last visit: 11/08/08]
41 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter
9. Annex I
42 Installation of a Solar Collector
Lydia Pforte - Emilie Girard Folkecenter