The laws of supply and demand apply to almost any product or service. That's true when you're trying to find strawberries in the middle of winter. It's just as true if you want to find someone to drill 500' (152 m) boreholes in an area where drillers only own drill rigs designed to drill to a depth of 300' (91 m). To build a GHX that only contractors from two states away have the equipment to build will almost always cost more to build than a GHX that can be built by local contractors.
A GCHP system, by definition, transfers energy to and from the ground. Obviously the temperature of the ground, thermal conductivity and diffusivity of the ground have an impact on how much and how quickly energy can be transferred between the fluid circulating through the GHX and the ground. The geology has an impact on how how much land area is needed to build it and how expensive it will be to build.
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.
If you lived in Canada or the northern States you're probably not looking forward to another winter after the record cold and snow we experienced. Winnipeg, MB had the coldest winter since 1898! That erased most of the memories we had from only two years earlier when we had one of the warmest years on record. What happens to a GHX when we go through extreme weather events like that?
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.
What' an NFAT? It's an acronym for a process to consider the Need For and Alternatives To the proposed and preferred option Manitoba Hydro has put forward. That preferred option is the construction of the Keeyask Dam ($6.95 billion), Conawapa Dam ($10.2 billion) and the Bipole III transmission line ($3.8 billion). MB Hydro claims these structures are needed to meet their forecast of the annual increase in electricity demand of 1.5%, or 80,000 kW every year for the next 20 years.
Architectural and engineering firms purchase insurance to protect themselves for errors that may occur on a project. Many commercial building projects require general contracting firms and mechanical contractors are covered with a surety bond or bid bond to ensure the project is is completed as designed. Large commercial projects are complex to build and unforeseen difficulties can happen that delay construction or create situations that are expensive to remedy.
During the last number of years, Manitoba Hydro, a government owned utility, has been proposing the construction of a number of large hydro-electric dams. Wuskwatim was completed in 2012 at a cost of $1.3 billion, produces 200 mW of power. Keeyask will cost $6.95 billion, will produce 695 mW at peak power and 4,400 gWh annually, and is slated for completion in 2019. Conawapa is larger. It is projected to cost $10.2 billion. will produce 1,485 mW at peak power, 7,000 gWh annually and is to be completed by 2025. To get the power to where it is needed, the 1,384 km Bipole III is to be built at a cost of about $3.8 billion. Total projected cost: over $22 billion...a cost of about $9,250 per kW, or $9.25 per W
Proponents of solar PV systems often talk about the "cost / Watt" to install photo-voltaic cell systems. The cost has come down considerably in the last few years, and now averages in the range of $5.90 per Watt. It's come a long way...it was around $10.00 / Watt a number of years ago. How does that compare to a GCHP system?
A GHX is an integral component of a GCHP system (hence the name "ground coupled). But in many commercial buildings there are times when there is cooling and heating going on at the same time. The center core of a building without any external walls or roof can require cooling because of internal gains (lighting, electrical equipment, occupancy) while the perimeter of the building may need heating. At times the amount of heat rejected to the GHX by one heat pump balances the amount of heat extracted from the GHX. The net effect on the GHX is zero. So why circulate fluid through the entire 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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