Wallkill Correctional Facility's 1.6 million BTU Solar Thermal Project
Project: Large commercial building retrofitted with solar thermal system
Goal: To reduce energy costs and act as a pilot project for other state facilities
The New York State Office of General Services (OGS) is the agency responsible for all public buildings in the state, including schools, prisons and government buildings. OGS Commissioner John C. Egan knew that through those buildings, his agency could realize enormous savings in energy costs. He just needed a pilot project to show how a move to renewable energy sources could save the state money while reducing greenhouse gas emissions.
The number of possible buildings to showcase is staggering, and which type of renewable energy source to implement depends on many factors. But ultimately Egan and his staff turned their focus to the Wallkill Correctional Facility and addressing their significant need for hot water with a solar hot water, or thermal, system.
The Challenge
The 608-bed medium-security Wallkill Correctional Facility, located about 80 miles south of Albany, dates back to the early 1930s. It's a sprawling complex of buildings totaling over 500,000 sq. ft. It also has a huge hot water demand-mainly for laundry, cooking, and showers-which was being fuelled by an oil-fired steam heat system. In the course of a year, that system burned through about 54,000 gallons of oil, according to Tom Varelli, Energy Conservation Technical Specialist, in Facilities Planning of the NYS Department of Corrections and Community Supervision.
The Solution
People have been heating water with sunlight for thousands of years and modern solar hot water systems are built on the same principles as the earliest systems, with a few significant improvements. Today, there are principally two types of solar hot water, or thermal, systems: evacuated tubes or flat panels. Both systems are based on the fact that black objects absorb the sun's radiation. Beyond that, the issues are keeping those black objects hot (reducing conduction, convection, and radiation to the ambient air); circulating water, or antifreeze, through them; and keeping the water or antifreeze hot.
Evacuated tubes use the principle that convection, a significant source of heat loss, does not occur across a vacuum. By piping water or antifreeze through a copper tube inside two concentric tubes with a vacuum between them, the fluid in the copper tube heats up with minimal heat loss back to the environment. Flat plate collectors look much like photovoltaic panels from a distance (indeed, it's possible to have both electricity and hot water in one system, but the efficiency is somewhat less than a single-type system), but instead of silicon collectors, they have absorber fins and pipes running vertically through them from a main inlet pipe at the bottom to a main outlet pipe at the top. Water or antifreeze flows from the inlet pipe up through the heat fins and out the top pipe to the house. In both systems, heat exchangers are often included to increase the fluid temperature as needed, and/or they are put in line with a conventional electric or liquid fuel-fired water heater.
Choosing one system or another is often a matter of preference. Flat plate collectors are typically more efficient than tube collectors in full sunlight but they lose their efficiency more quickly when skies are overcast. They are also less prone to damage from things like small tree limbs and hail and tend to last longer than tube collectors, which can lose their vacuum over time.
OGS engineers worked with SunMaxx Solar Thermal, based in Conklin, NY, just south of Binghamton, to design the system. What they ultimately came up with was a system totaling 1440 evacuated tubes that would produce an average of 1.6 million BTU's per day. Over the course of a year, that would tackle about 10 percent of the facility's need for oil for heating water. It would also offset about 62 tons of carbon dioxide, each year, in the process.
Results and Future Plans
The project, nicknamed Project Sunshine, kicked off with a $270,000 grant from the New York Power Authority (NYPA), which went a long way toward meeting the $343,000 price tag. It went on-line in January 2010, becoming the largest solar thermal installation of its kind in the eastern US. The project is expected to pay for itself in 20 years, and have a life expectancy of more than 30 years.
In June 2010, the project was honored as the Best New York State Government Solar Project of the Year by the NYS Solar Energy Industries Association at their annual conference in Albany.
According to Commissioner Egan, based on the pilot project's performance thus far, plans are to replicate it in other state facilities, which could include correctional facilities, hospitals, and college campuses. And NYS Department of Corrections and Community Supervision Commissioner Brian Fischer has said that his agency is planning to add solar thermal systems to more of the 68 prisons across the State.
