Tag: Geothermal

Smithtown, N.Y. Adopts Model Geothermal Energy Code

Apr 13 – McClatchy-Tribune Content Agency, LLC – Brian Heaton Government Technology

Smithtown, N.Y., is the first town on Long Island to adopt a model code for the installation and use of geothermal energy systems.

Developed by the Suffolk County Planning Commission, the geothermal rules outline building standards and requirements for those wanting to adopt the underground-based green energy option. Smithtown Town board members adopted the policy 4-0 on March 19.

Geothermal energy siphons below ground temperatures of the Earth to heat and cool homes and other structures. Three types of geothermal systems are addressed in the code — closed loop, where plastic pipe exchanges heat with the ground with water or a water and chemical mixture; open loop, which uses water wells; and a direct exchange, which uses buried copper tubing to conduct energy with the ground using a refrigerant.

In an interview with Government Technology, David Calone, chairman of the Suffolk County Planning Commission, said the geothermal model code took about seven months to fully develop. The commission partnered with the Long Island Geothermal Energy Organization (LI-GEO) to draft the rules, which were published last November.

The commission used the template from other green energy codes as a template for geothermal, but environmental issues were a concern. Calone explained that the biggest issue in geothermal is the use of chemicals in the pipes. While the chemicals are self-contained, the commission restricted the use of several kinds of liquids that would be potentially harmful to groundwater.

Suffolk County’s primary water supply is three aquifers on Long Island.

The geothermal code follows on the heels of the commission’s model codes on solar and wind energy, which have either been adopted or are being considered across the New York state. Solar installations have exploded in recent years following the county’s model code introduction and Calone hopes a similar trend will happen with geothermal.

Cost may be a problem, however. Residential geothermal systems are expensive, averaging about $30,000 depending on the size needed, according to a local utility. But rebates from the local power company and the government may help make geothermal more feasible for Long Islanders.

“Right now, our local utility, like many utilities, incentivizes solar and wind — not geothermal,” Calone said. “However, they’ve stated their intentions to do so, so this is a situation where we can get a little ahead of the curve.”

Looking ahead, Calone said he expects other towns in Suffolk County will follow in Smithtown’s footsteps and adopt the commission’s geothermal planning code. He noted that the Town of Brookhaven is “there and ready to pass it,” while Riverhead, Islip and Huntington are all looking into the issue.

“They had some little things they are thinking about from an inspection perspective, but they’re very interested in doing it,” he said.

Brian Heaton — Senior Writer

Brian Heaton is a senior writer for Government Technology. He primarily covers technology legislation and IT policy issues. Brian started his journalism career in 1998, covering sports and fitness for two trade publications based in Long Island, N.Y.

Knight-Ridder

 

Geothermal Heat Pump Basics

Geothermal heat pumps (GHPs), sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps, have been in use since the late 1940s. They use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies (300% to 600%) on the coldest winter nights, compared to 175% to 250% for air-source heat pumps on cool days.

Although many parts of the country experience seasonal temperature extremes — from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth’s surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.

As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.

A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These appliances combine the best of both systems. Dual-source heat pumps have higher efficiency ratings than air-source units, but are not as efficient as geothermal units. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and work almost as well.

Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5 to 10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.

TYPES OF GEOTHERMAL HEAT PUMP SYSTEMS

There are four basic types of ground loop systems. Three of these — horizontal, vertical, and pond/lake — are closed-loop systems. The fourth type of system is the open-loop option. Which one of these is best depends on the climate, soil conditions, available land, and local installation costs at the site. All of these approaches can be used for residential and commercial building applications.

CLOSED-LOOP SYSTEMS

Most closed-loop geothermal heat pumps circulate an antifreeze solution through a closed loop — usually made of plastic tubing — that is buried in the ground or submerged in water. A heat exchanger transfers heat between the refrigerant in the heat pump and the antifreeze solution in the closed loop. The loop can be in a horizontal, vertical, or pond/lake configuration.

One variant of this approach, called direct exchange, does not use a heat exchanger and instead pumps the refrigerant through copper tubing that is buried in the ground in a horizontal or vertical configuration. Direct exchange systems require a larger compressor and work best in moist soils (sometimes requiring additional irrigation to keep the soil moist), but you should avoid installing in soils corrosive to the copper tubing. Because these systems circulate refrigerant through the ground, local environmental regulations may prohibit their use in some locations.

HORIZONTAL

This type of installation is generally most cost-effective for residential installations, particularly for new construction where sufficient land is available. It requires trenches at least four feet deep. The most common layouts either use two pipes, one buried at six feet, and the other at four feet, or two pipes placed side-by-side at five feet in the ground in a two-foot wide trench. The Slinky™ method of looping pipe allows more pipe in a shorter trench, which cuts down on installation costs and makes horizontal installation possible in areas it would not be with conventional horizontal applications.

Illustration of a horizontal closed loop system shows the tubing leaving the house and entering the ground, then branching into three rows in the ground, with each row consisting of six overlapping vertical loops of tubing. At the end of the rows, the tubes are routed back to the start of the rows and combined into one tube that runs back to the house.

VERTICAL

Large commercial buildings and schools often use vertical systems because the land area required for horizontal loops would be prohibitive. Vertical loops are also used where the soil is too shallow for trenching, and they minimize the disturbance to existing landscaping. For a vertical system, holes (approximately four inches in diameter) are drilled about 20 feet apart and 100 to 400 feet deep. Into these holes go two pipes that are connected at the bottom with a U-bend to form a loop. The vertical loops are connected with horizontal pipe (i.e., manifold), placed in trenches, and connected to the heat pump in the building.

Illustration of a vertical closed loop system shows the tubing leaving a building and entering the ground, then branching off into four rows in the ground. In each row, the tubing stays horizontal except for departing on three deep vertical loops. At the end of the row, the tubing loops back to the start of the row and combines into one tube that runs back to the building.

POND/LAKE

If the site has an adequate water body, this may be the lowest cost option. A supply line pipe is run underground from the building to the water and coiled into circles at least eight feet under the surface to prevent freezing. The coils should only be placed in a water source that meets minimum volume, depth, and quality criteria.

Illustration of a pond or lake closed loop system shows the tubing leaving the house and entering the ground, then extending to a pond or lake. The tubing drops deep into the pond or lake and then loops horizontally in seven large overlapping loops, then returns to the water's edge, extends up near the surface, and returns back to the house.

OPEN-LOOP SYSTEM

This type of system uses well or surface body water as the heat exchange fluid that circulates directly through the GHP system. Once it has circulated through the system, the water returns to the ground through the well, a recharge well, or surface discharge. This option is obviously practical only where there is an adequate supply of relatively clean water, and all local codes and regulations regarding groundwater discharge are met.

Illustration of an open loop system shows a tube carrying water out of the house, into the ground, and over to a well, where it discharges into the groundwater. A separate tube in a well some distance away draws water from the well and returns it to the house.

HYBRID SYSTEMS

Hybrid systems using several different geothermal resources, or a combination of a geothermal resource with outdoor air (i.e., a cooling tower), are another technology option. Hybrid approaches are particularly effective where cooling needs are significantly larger than heating needs. Where local geology permits, the “standing column well” is another option. In this variation of an open-loop system, one or more deep vertical wells is drilled. Water is drawn from the bottom of a standing column and returned to the top. During periods of peak heating and cooling, the system can bleed a portion of the return water rather than reinjecting it all, causing water inflow to the column from the surrounding aquifer. The bleed cycle cools the column during heat rejection, heats it during heat extraction, and reduces the required bore depth.

LEARN MORE

via Geothermal Heat Pumps | Department of Energy.