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HVAC Thermal Storage Practical Application and Performance Issues by Andrew Seaman, Andrew Martin, and John Sands | PDF Free Download.
Tlicrinal storage. (11- energy storage. is defined as the charging and discharging of; I store of finite thermal capacity in response to the flow of Iicat to and from the system where supply atid denied for heat are out of phase.
When the energy store operates as a source of heat the process is known: is heat storage and when it acts; it is a sink it is known as cool storage. Storage inlay involves energy collection from the sun, ground, air, or water.
Air and \vater (01- \vater mixtures) are typically used for transporting energy to and fi-om the store. The storage/discharge cycle is dependent on the building load and the availability of energy to be stored for later use.
Most systems use a daily cycle, although weekly and scansorial cycles: ire also used. Active thermal storage systems (where additional mechanical systems; ire added as part of the thermal storage system) typically offer a high degrcc of control of the internal environment.
Some active systems, such as ice thermal storage, store energy bvheii it is available at a lower cost ready for- use during higher tariff periods. These systems are c generally considered to 'load shift' rather than to conserve energy.
Other active systems. IS acti\,e solar Indicating, store energy when it is readily available for later use and are thus reducing deinaiids on fossil fuels that for -in the energy supply (gas, electricity, oil) into a building. Passive systems. such; is passive night cooling or passive solar heating 'tcinpcr' the internal environment and: ire, therefore, less precise in the decaf comfort control provided.
They're; also used to attenuate loads where active system arc cinployed. Passive systems generally benclit foin \'cry low running costs.
'Hybrid' or 'semi-passive' systems. such ;is gound cooling loops. use amounts of the plant (eg heat pump) to increase or reduce the teinperatiire of the 'passive' energy supply. In this way, thcnnal comfort in the occupied space is improved. Examples of each system type are shown in Table I.
Tlie ASHRAE Applications Handbook lists the benefits of triennial storage; Is follow s:
Equipment six can be reduced due to the use of the thermal store to infect pal-t. or all of the design cooling load.
Where plait is used to change the thermal store (CG:I chiller) it can operate continuously, if necessary. to cither charge the thermal store or to help to meet the load directly during peak periods. in conjunction with the store.
Thus, smaller plmtcui be installed to meet the same overall design load. The reduction in plant size may also allow a reduction in electric cable sizes producing further capital cost savings.
Other cost savings call be realized by using electricity and other fuels during low tariff periods to drive the plant s~ipplyiiig the thermal store.
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