In 1990, Squaw Valley had a diesel fuel spill that cost a million dollars. In November of 1991, a 20,000-gallon propane tank near a locker room leaked for two days. "We had to close the area all around it at the base of the mountain," says Squaw engineer Hardy Herger Ph.D.

Herger knew that there were better ways to heat Squaw’s buildings, for less money and without volatile fuels—from heat sources that are available to every ski resort either free, or, at most, dirt cheap: cogeneration and ground source heat pumps, a form of geothermal energy.

Ground source heat pumps may be the most under-utilized energy-saving devices around. They work by using the constant temperature of the earth to either heat (in winter) or cool (in summer) via a heat exchange system, much like that used in a refrigerator or air conditioner. (See box for details.) They have few moving parts, which makes them very reliable and long-lived. "The world’s first heat pump was built in 1906 in Zurich, Switzerland, and it still works as a museum piece,” Herger notes.

The heat source for a heat pump is the earth itself. “When you get more than six feet below the surface of the ground, the temperature is about a constant 45 degrees Fahrenheit year-round—heat which can easily be captured with a heat pump,” says Herger. There are four basic types of pumps, based on how the energy of the earth is harnessed: water-to-water, water-to-air, air-to-water, and air-to-air.


Geothermal Energy
In 1992, Squaw installed its first geothermal system, in the Squaw Kids building. It uses four 12-ton ground source water-to-water heat pumps. The system takes heat from the earth via a network of in-ground pipes. The liquid in two 12-ton units is glycol, which flows through seven loops (ground collectors) of 1-inch pipe, each loop of which is 1,500 feet long. The other two 12-ton units are filled with methanol and the in-ground loops consist of 30,000 feet of 3/4” SDR 35. The entire 4 x 12-ton system provides plenty of heat for the 15,000-square-foot building and 8,000 square feet of snowmelt for walkways. The average heating cost per day is less than $25. In summer, a flick of a switch reverses the process and the heat pumps can be used for cooling.

Why haven’t heat pumps become the norm, then? Well, there’s the initial cost. Installing a geothermal heat system requires placing tens of thousands of feet of pipes at least six feet below ground level. But there are also ways to keep the installation costs down. The lines can be placed in a grid pattern of almost any shape, for example. (They can also be placed vertically, like the lines for a well.) Using coils rather than straight pipe also reduces the amount of excavation needed, but the coils still require considerable space.

However, Squaw was laying a series of other in-ground lines (high-voltage, gas, and telecommunications) at the time. So, Herger had the ditches made a foot wider, and put his collector pipes next to the utility lines, at very little extra cost. The only limitations were that the collectors had to be at least six feet below the surface and at least one foot from the other lines.

In 1992, there was little experience with the use of either of these types of geothermal systems at altitude. That’s partly why Herger installed two different types of systems—to double his chances that the concept would work as it should. But Herger has found no negative side effects or operational problems; both systems have worked well. Since methanol is about four times cheaper than glycol, though, that system is more economical.


The Hybrid System
Squaw’s second system using heat pumps was built in 1997. This system is unique. It draws heat from the two 1,000 hp electric motors that power Squaw’s Funitel and feeds it into two 5–ton air-to-water heat pumps. The system heats the floor and the stairs of the 5,000-square-foot building, as well as its 600-square-foot snowmelt system. At night, after the Funitel shuts down, a 12-ton water-to-water heat pump starts automatically and serves the same purposes.

“One of the most wasted source of heat at ski resorts,” says Herger, “is the heat from lift motors. Buildings as far as three or four hundred feet from the lift motors can be heated with the heat from the engines, so long as the pipes connecting the two locations are well insulated.”


Practical Sense
Because of the dynamics of the heat pump, the water comes out of the heat pump at 160 degrees—so the system can be used to heat water as well as space, according to Herger. For hydronic floor heating, the water temperature only needs to be about 90 to 95 degrees Fahrenheit.

Herger said that capturing heat through ground source heat pump systems has saved Squaw about 50 percent compared to the cost of heating with propane. Plus, the heat pump system produces less pollution, and staff don’t have to work with volatile fuels. The system also uses about 30 percent to 50 percent less energy than electrical heat. If a building is receiving its heat from the lift motor, the savings are much, much greater—the heat is practically free.

Herger recommends that anyone interested in this technology should consult with an experienced contractor. Those used to be rare, but their ranks are growing as the push for greater efficiency and lower energy costs gathers steam.

How a Heat Pump Works
Heat pump technology relies on The Second Law of Thermodynamics, which effectively means that if a cold object is placed next to a hot object, the cold object will become warmer and the hot object will become cooler. A refrigerant works by drawing heat away, leaving the surrounding area much colder. The fluid in a heat pump works by absorbing warmth from the earth around it.

In the refrigerator: An electric compressor compresses the gas into a liquid, which is then allowed to evaporate. Evaporating ammonia, often used in refrigerators, for example, is minus 27 degrees F.

The compressor forces the gas through an expansion valve, where it becomes a very cold mist flowing around the inside of the coils in the refrigerator. The cold draws the heat out of the food.

The compressor then recompresses the mist, creating heat, which is released and dissipated through coils on the back or bottom of the refrigerator, and the process keeps repeating itself.

In a ground source heat pump, the refrigerated coil draws the heat out of a closed-loop collection system that brings 45 to 50 degree heat out of the earth. Since the refrigerant is much colder than the earth, it easily draws heat from the 45- to 50-degree earth around the loop. But instead of expelling the heat as waste (as a refrigerator does), the heat is captured through a second system of closed coils and used for heating.

Heat pumps are designed so the system can be reversed to provide air conditioning. In that case, they remove the heat from buildings and send it back into the ground, where it dissipates. Then the cooled liquid or gas is recirculated to the heat pump, which transfers the cooling to the air-conditioning system.