Walmart stores recently built their first new store built with 100% LED lighting in South Euclid, OH. In addition to the LED lighting, lighting controls use sensors to take greater advantage of daylighting in the store and daylight harvesting to reduce energy use for lighting by a further 25%. In addition to the lighting changes, the store boasts a white membrane roof to reduce solar heat absorption. These measures, combined with efficient air conditioning systems make it one of their most efficient stores. These measures help make the integration of a GCHP system even easier.
Lowering internal heat gains by 1 Watt per square foot in a 120,000 square foot (11,150 m2) store reduces the cooling loads by approximately 120 kW (34 tons). In a store that's open 24/7, that reduces the heat rejection to a GHX by 3.6 million kBtu every year, plus compressor heat, for a total of 4.5 million kBtu. A store like this is cooling dominant, even in a fairly cold climate. That means the changes to the cooling load can reduce the size and cost of a GHX for a GCHP system significantly.
This creates some interesting implications. The land area needed for a GHX is reduced. In some projects, the size of the GHX may be reduced enough to allow the GCHP system designer to consider a horizontal GHX rather than a vertical GHX...resulting in a cost reduction of 25% to 40% depending on the site and geology.
Reducing the heat gain from lighting also increases the heating load. Heat not supplied by the lighting must now be supplied by the heating system. Increasing the heating load while reducing the cooling load helps balance the energy loads to and from the GHX. This further reduces the size of the GHX
Walmart has experimented with a GCHP system in at least one store in Brantford, ON. Taking a holistic approach to the entire building and systems can make it more affordable to consider the installation of a GCHP system. The additional cost of installing efficient lighting is offset by the reduced size, possibly the configuration and cost of the GHX.
In my blog I'll be expressing my opinions about what I've the learned about ground coupled heat pump (GCHP) systems over the last 30 years. I've been very fortunate to work with many interesting people who are passionate about this technology...engineers, geologists, mechanical contractors, drillers, excavation contractors...in different parts of the world. I've learned a lot from them and will be using this forum to pass on some of the things I've learned and feel are important. Please feel free to use this information if you feel it's worthwhile...hopefully you can avoid some of the same mistakes I've learned from.
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