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The thermal storage air conditioning system

activates heat pumps during the night whenenergy demand is low, in addition to daytime

hours when the building is supplied with

conditioned air, to store thermal energy in the

form of chilled water, ice and hot water so that

they can be used during the day.

An extremely efficient system can be built by

combining thermal storage with high-efficiency

heat pumps.

With conventional air conditioning systems that

do not use thermal storage, equipment is shut

down completely during the night and the heat

pump is activated during the day to supply hot

and cool air.

On the other hand, with thermal storage air

conditioning, heat pumps are activated during

the night when energy demand is low to store

thermal energy in thermal storage tanks.

Chilled water and ice are stored in the tanks for

cooling purposes, and hot water for either

heating or hot water supply.

During daytime of the next day when demand is

high, thermal energy is drawn from the thermal

storage tank for cooling, heating or to supply

hot water.

The most appropriate type of thermal storage air conditioning system such as water-type or ice-type

system can be selected depending on the scale and size of the installation space.

Water thermal storage system

Underground space which is usually left unused (underground pit) is used as the water thermal storage tank.

The water in the thermal storage tank can be used for extinguishing fires or for domestic use during

disasters or emergencies.

Ice thermal storage system

Ice is made in the thermal storage tank to store cold energy.

The tank size can be kept smaller than with water thermal storage tanks.

Features

Basic Concept or Summary

Thermal Storage Air Conditioning System

Keywords X2 office Y2 device Z2/ 3 oil R government

Heat Pump & Thermal Storage Technology Center of Japan

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Conventional Air Conditioning

Building is cooled during

the day by external motors.

Does not operate at night.

Heat Storage Air Condition

Thermal energy is stored

in a thermal storage tank.

The heat source unit runs on lessexpensive nighttime electricity andstores chilled water (ice) during thesummer and warm water in the winter.

Energy in the thermal

storage tank is used for

heating and cooling.Air condition uses chilled water (ice)and warm water from the thermalstorage tank during the day.

Water thermal storage system Ice thermal storage system

Water pipe Water pipeHeat sourceunit

Heat sourceunit

Air duct

Air duct

Air duct

Air duct

Air conditioningunit

Air conditioningunit

Underground slabUnderground slab

Thermal water tank Thermal ice tank

Day

DayNight

Night

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Installation in Practice or Schedule

Effects or Remarks

Contact: Heat Pump and Thermal Storage Technology Center of Japan

1-28-5 Kakigaracho F Bldg., 6F, Kakigaracho Nihonbashi, Chuo-ku, Tokyo, Japan

Tel: 03-5643-2401 Fax: 03-5641-4501 http://www.hptcj.or.jp/about_e/

Domestic Total no. of installations: 27,807 (2007)Peak shift effect in domestic power demand from thermal storage air conditioning system

installation: 1.73 million kW (2007)

Overseas Installed at numerous large buildings and regional cooling and heating plants in the US. In

recent years, also installed at airports and regional cooling and heating plants in China.

However, no small-size systems.

The thermal storage air conditioning system responds

to peaks in cooling loads during the day by combining

cold energy stored during the night with that produced

during daytime. Consequently, the size of the

installation capacity can be kept to almost half that of

systems that do not utilize thermal storage.

Energy efficiency

Energy consumption is curbed significantly by combining high-efficiency heat pumps with thermal

storage.

Cost efficiency

Energy efficiency also reduces energy costs.In Japan, a discount applies on nighttime electricity tariff. This reduces energy costs further.

Japan has a subsidy system for promoting the use of thermal storage air conditioning systems. This can

be utilized to reduce initial investment burdens.

Environmental preservation

Being energy efficient, CO2 emissions can be curbed considerably.

Wider use of environment-friendly thermal storage air conditioning systems will help alleviate peaks in

power use and eliminate the need for construction of new power stations.

Coolingload forone day

Generates cold

and stores it

Stored

cold

energy is used

Generates cold

for immediate use

Size

ofequipment

capa

cityrequiredwithout

thermalstorage

Lesssystem

capacity

Equipm

ent

capacitywhen

usingthermal

storage

Cooling time

Units

Eco-Ice MiniEco-Ice (Individual distributed model: Min. 10 hp)Eco-Ice (Central model)Thermal storage