chapter 12: alternative technologies to be used with the guide to building energy efficient homes in...
TRANSCRIPT
Chapter 12: Alternative Technologies
To be used with the Guide to Building Energy Efficient Homes in Kentucky
Alternative Technologies
Alternative Technologies
Solar Hot Water
Key concept:
Reduce gas or electric
requirements to produce hot water
Use sun’s energy to heat or preheat
water
Solar Hot Water System
Solar Collector
Storage Tank
Solar Hot Water System
Solar Hot Water System
Solar Hot Water System
Active Passive
Systems
Active • Relies on pumps and
valves to circulate the water or heat exchange fluid through the solar collector
Passive• Relies on the natural
tendency of water to rise when heated, and thereby circulate through the system
Systems
Active • Slightly more
complicated• More flexible in
placement of the components
Passive• Simpler– Lack of pumps
• Placement of components dependent on the physics of hot water buoyancy
Direct Systems
Closed Loop Solar Hot Water System
Drain Back System
Drain Back System
• The drain back system uses water as the heat exchange fluid– Freeze protection – pump
shuts off when the temperature of the collector cools below that of the tank• Water “drains back” into storage
reservoirs
Passive Systems
Thermo-siphon system uses the tendency of water to rise as it is heated.
Passive SystemsCooler bottom
tank water flows down
pipes to bottom of collector
Heated water
becomes lighter and
flows up and into
the top of storage
tank
Passive Systems
The integral collector storage system has the storage tank integrated into the solar collector.
Passive Systems
Cold water supply is connected directly to the collector
Sun heats this water, which remains in the panel until needed
Design Considerations
• Solar collectors should be placed on the south side
• Install a mixing valve• Install a back-up heat
system
Photovoltaic Panels
Photovoltaic (PV) panels are a way to generate on-site energy• High cost
Photovoltaic System
Design Considerations
Design of PV systems can affect the performance• Location• Angle of the collector• Internal losses• Shading• Temperature
Design Considerations
• Variations within 15 degrees of true south – OKBeyond 15 degrees – lose performance
• Set the tilt to maximize the summer solar incident angleDifficult to do if considering aesthetics
Design Considerations
• Locate panels in shade-free areas
• Panels need to be clean of dust, leaves, snow
• Temperature affects the performance of the PV panel– Keep as cool as possible
Summary
Summary