A building with a well designed GCHP system uses about 60% to 70% less energy for heating, cooling and domestic hot water than the same building built with a conventional fossil fuel heating system and a conventional air cooled chiller. If the system integrates other renewable technologies and thermal energy storage, energy use can be reduced even more. With concerns about climate change (whether it's real or not), more building owners and developers are making changes to the way their buildings are designed.
I've often seen a tender for construction of a GHX that specifies the GHX must be designed to supply "xxx" Btu's or kWh of energy based on a peak cooling load of "xx" tons or kW and a peak heating load of "xx" Btu/h or kW. In most cases little additional information is provided - not the area of the building, what the building is used for, how it's constructed... nothing else. Designing a GHX based on that information is impossible.
We had an interesting discussion about how the design of a GCHP system compares to the design of a GCHP system in the Certified GeoExchange Designer (CGD) class in the IGSHPA classes in Stillwater this week. The question about why the design of a photo-voltaic cell system could be so easily standardized, while the design of a GCHP system is so site specific and is difficult to standardize. We came up with a few reasons that the design process is more onerous for a GCHP system.
How hard a heat pump compressor has to work is directly proportional to the "temperature lift" it has to produce. The greater the temperature lift, the harder the compressor has to work and the more power is needed to run it. Looking at the compression ratio the compressor has to achieve to produce the desired temperature to deliver the heating or cooling required is the compression ratio of the compressor.
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.
Amory Lovins of the Rocky Mountain Institute has long advocated the concept of "negawatts". For some reason many people have difficulty equating reduced energy consumption as having the same value to a utility as generating new energy... especially the people running the utilities. Think about it. If you reduce electricity in your home by religiously turning off lights that don't need to be on and reduce your energy consumption by 1,000 kWh this month, those 1,000 kWh can be sold to another consumer. Is that any different to the utility than building a generator to produce 100 kWh to sell to that other consumer? Actually, it is....
Energy modeling is usually considered time consuming and it's tedious. One of the primary reasons it's done at all in many architectural and mechanical engineering offices is simply to comply with LEED, the building code or various incentives. All too often the person tasked with developing the energy model is the least junior technician or engineer in training in the office...the person with the least experience about buildings and systems, and how they can impact the energy loads. Energy modeling, when used as the design tool...
If you look for it, you'll find a lot of "waste" heat in some buildings...and owners or tenants are paying a lot of money to get rid of it. At the same time they are paying a lot of money to purchase energy from a utility to heat their building. What a waste! Buildings are used for many different kinds of activities. Many of these activities and the equipment...
You might have been told that if your building is already well insulated and energy efficient there's not much point in considering a GCHP system. There simply wouldn't be a payback because of the cost of installing a GCHP system and GHX is so high that I'd never get a return on my investment. I'd like to dispel that myth!
Building and project developers are all about getting a project from paper to a built reality. And they're about making money on projects. To make a profit, they have to keep an eye on the budget they've been given to work with. Something that adds cost to the project generally has to be balanced by cost saving in another area, or has to provide greater value, or it won't be considered. So how can we, as geothermal designers and contractors, install systems with no additional cost, or add enough value for a developer to consider a GCHP system for a project?
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.