EnLink Geoenergy Services:

Applying Innovation to Geothermal Systems

Back in the early 1990s, Tom Amerman had worked for many years in the oil and gas industry when a light went off in his mind. He saw how technologies used in his industry could be applied to another arena, that of geothermal energy. His vision would pan out. Applying sophisticated oil field drilling techniques, he created EnLink Geoenergy Services in 1995, and his firm has gone geothermal in a big way.

Geothermal systems use the earth's constant temperature, usually in the 50s F., as a source of energy for heating and cooling buildings. Experts regard this as one of the most energy-efficient, environmentally clean, and cost-effective sources of renewable energy.

Based in Houston, Texas, EnLink designs and installs geothermal heat pump (GHP) systems in institutional and commercial buildings. As a turnkey system provider, the company designs and builds both the exterior part of the geothermal system and the inside installation. “We’re a design-build contractor that does a lot of R&D and makes its own tools to give it a competitive advantage technologically,” states Greg Tinkler, director of engineering.

The process for installing a geothermal system starts with a series of holes drilled hundreds of feet in the earth using standard drilling rigs used for water wells. EnLink then inserts into each hole two polyethylene pipes one to two inches in diameter and joined at the bottom to form a loop. Near the surface, the pipes join to a common manifold to combine loops to form a continuous circuit that allows water (sometimes mixed with antifreeze) to flow to the bottom of each sunken loop. From the manifold, interior piping is run to a heat pump inside the building. In this, the fluid flows through a heat exchanger to warm or cool refrigerant to provide warm or cool air as needed in individual zones throughout the building.

Geothermal systems offer several advantages. They use considerably less electrical power than conventional HVAC systems; EnLink says its system reduces power use by 40 to 70 percent. The systems also provide cleaner air and reduce maintenance, largely because conventional HVAC systems have components such as air handling units located outdoors with long ducts to deliver air inside to individual rooms. The machines are exposed to the weather, and the ducts are prime breeding grounds for allergenic molds and spores. System’s such as EnLink’s have the heat pumps placed in closets, ceilings, or as consoles in each room, requiring ducts but a few feet long, minimizing the health risk from airborne bacteria. This also allows more precise individual room temperature control.

Simply put, Tom Amerman looked at the equipment used in directional drilling for oil and gas and made it smaller for geothermal use. Beginning with a device they call the Coil Tubing Unit (CTU) as a pivotal concept, EnLink created processes to install loop fields in the earth more quickly and efficiently than conventional methods. Typically, geothermal companies have used brute manpower to force tubing loops to the bottom of a drilled hole or tied steel weights to it to pull it down along with a trimmie pipe used to pump grout to fill the hole after the polyethylene loop is in place.

The unique CTU consists of a roll of 1.25-inch diameter steel tubing whose end seats in a specially made U-bend that forms the bottom of a loop and pushes it to the bottom of a hole as the CTU and polyethylene tubing simultaneously uncoil. Once the pipes reach the bottom of the hole, the CTU pumps thermally conductive grout from the bottom to the surface as it withdraws.

Because the CTU doesn’t require a weight, you can drill a 3.5-inch-diameter hole instead of the usual 5-inch hole. Smaller hole size increases loop efficiency up to 25 percent because heat passes through a thinner wall of grout. Less footage is required in a given installation to achieve the desired heat transfer level.

“Most of our client base seems to be K through 12 schools and universities. A lot of it right now seems to be in the southwest U.S.,” Tinkler says. “We’re focusing more on Texas, New Mexico, Colorado, Nevada, and California.” The company targets areas where utilities are having electrical grid problems and trying to get their demand down.
As an example of a typical installation, they recently installed a geothermal system for the Santa Teresa Middle School, part of the Gadsden Independent School District in New Mexico. The retrofit project involved 100,000 square feet in two buildings on the campus.

Previously, the HVAC system consisted of evaporative cooling and gas heating, which caused problems with uncomfortable temperatures in hotter months, high humidity levels, and sand infiltration. The installation required more than 200 vertical boreholes 400 feet deep and 100 GHP units with a total capacity of 400 tons. Each classroom has an individual heating and cooling unit, thermostat, and fresh air system. Electricity use was reduced up to 40 percent, and up to 90 percent of the school’s equipment rooms, previously used to house mechanical equipment, were converted to storage.

With 25 employees, EnLink has other facilities in El Paso, Texas; Bohemia, New York; and Atlanta, Georgia. They have a manufacturing plant in Atlanta that injection molds U-bends for tubing loops and builds tooling dies. They also make their own CTUs and grout pumping equipment.

As director of engineering, Tinkler is responsible for the design, engineering, and as-built drawings of EnLink projects, including indoor mechanical systems as well as energy calculations and modeling of the geothermal systems. He also oversees developing and implementing the standards, processes, and tools EnLink uses. To accomplish all this, he has an engineering staff of five mechanical engineers and two geologists.
Tinkler says EnLink hires new engineers “once in awhile.” Currently, they’re looking for an electrical engineer to work out of the Houston office. “About 90 percent of what we do is retrofits instead of new construction,” he explains. “When a building has heating only, and you’re going to add cooling, you’re adding a load, and we’ve got to evaluate the electrical system to see whether it can handle the additional load.”

What does EnLink like in an engineer? They look for experienced engineers who “work more towards not just doing it, but doing it energy efficiently,” Tinkler says. Even if they don’t have a current opening, they peruse resumes anyway and hire the ideal person if one comes along. “If I had a mechanical come in who’s got some electrical experience, I’d probably hire them anyway.”

Fueling EnLink’s growth, public awareness of geothermal energy is rapidly increasing, as evidenced by the fact U.S. GHP shipments have increased by about 25 percent a year since the late 1990s. Tom Amerman now serves as chairman emeritus and has had to leave day-to-day operations due to illness. But he leaves knowing he transferred his skills from a fossil fuel industry to a renewable energy field, creating a company with a bright future.

Snapshot

Company: EnLink Geoenergy Services

Type: Engineering and construction firm specializing in geothermal heating and cooling systems for institutional and commercial buildings

Location: Headquartered in Houston, Texas with other offices in El Paso, Texas; Bohemia,New York; and Atlanta, Georgia

Contact information for submitting resumes:
Greg Tinkler, director of engineering
E-mail - gtinkler@enlinkgeoenergy.com

Website: www.enlinkgeoenergy.com

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Editor: Tom Gibson
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