| Abstract |
As for most renewable energy concepts, the low temperature ground-source heat pump (GSHP) systems make use of the solar energy stored in the Earth's crust, and are attractive alternatives for heating and cooling commercial and institutional buildings in cold and very cold climates. They offer the possibility of using other free, inexhaustible and ecological energy such as thermal and photovoltaic solar, building internal gains and exhaust air, and jacket and combustion gas heat recovery from backup gas-fired engines. These systems also provide additional energy savings since the heat recovered from zones requiring cooling can be transferred to zones with simultaneous heating demands. GSHP systems are reliable, provide high comfort levels and as lower peak power demand during both heating and cooling dominated periods. Today the main issue concerns the optimization the GSHPs mechanical design and controls strategies in order to reduce the capital costs and thus increase their market acceptance. Several design improvements of residential and large commercial and institutional GSHP systems have been implemented in Canada during the last decades. The vast majority of these improvements aimed at optimizing the geothermal fluid pumping and integrating multiple energy sources with thermal storage, thermal or photovoltaic solar captors, direct geothermal cooling and radiant floor for heating and cooling. Even if such improvements generally lead to reduced energy consumption, their capital and operating costs and technical feasibility have to be established for each particular application. Other improvements are still required in order to overcome technical barriers and increase the market accessibility of GSHP systems. This paper describes a number of innovative ground-source heat pump concepts operating in cold and/or very cold weathers as those of Canada, focusing on the system design and control improvements aiming at optimizing the seasonal performances and at reducing systems’ construction and annual energy costs. The ground thermal behaviour and heat recovery capability, as well as the main parameters and seasonal performances of each selected concept, are also presented. |