Renewable Energy: Solar Thermal
By Anne Cosgrove
Published in the November 2010 issue of Today’s Facility Manager
Systems that convert solar energy into heat (solar thermal) can be useful for facility managers (fms) trying to diversify where they source energy for building operations. These types of installations are most often used for hot water heating (including swimming pools), but facilities are also applying solar thermal for space heating and cooling purposes.
From an environmental standpoint, using solar thermal technology reduces the amount of fossil fuel energy a building consumes, thus lowering the greenhouse gas emissions that result from its operation. Economically, installing this type of system calls for a relatively substantial investment; however, financial incentives available to many facilities can reduce costs significantly. Additionally, by producing their own heat for certain facility operations, fms are able to stabilize the price they pay for the energy related to those uses.
The components of a solar thermal system can vary, but the basic equipment (normally placed on a roof or open land) centers around flat plate or tubular “collectors” that absorb and transfer the heat from the sun through piping that delivers the heat directly to its end use or to a storage tank.
The current growth rate for solar water heating (SWH) systems in buildings is high, and this is led by swimming pool applications. In the U.S., an estimated 200,000 commercial SWH systems have been installed to date, according to Bill Guiney, program director, Global Renewable Energy Department, Building Efficiency for Johnson Controls. These systems can provide up to 50% of most commercial applications for hot water, depending on location, he states.
While facilities in some geographic regions are in a position to “collect” more solar heat than those in other locales—as is the case with solar photovoltaic (PV) technology, a broad range of locations can benefit from solar thermal if other factors justify the investment. Among these considerations is the facility’s pattern of water usage. Solar thermal is usually found to be most cost-effective for facilities with a water heating load that is constant throughout the year and throughout the week (to use solar heat every day). For this reason, leading examples of facility types well suited for SWH are hotels, laundries, prisons, and kitchens.
On the financial front, fms can work with an energy expert to take into account how much a solar thermal system will cost, the energy price they currently pay for the intended application, and if there are financial incentive options (or other mechanisms, such as performance contracting) available to reduce capital outlay.
To date, commercial solar thermal in the U.S. has lagged behind solar PV systems (which convert solar energy into electricity). And part of the reason is availability of financial incentives; however, solar thermal is gaining more attention there. In October 2008, as part of the Emergency Economic Stabilization Act, the solar investment tax credit provision extended a 30% tax credit for solar installations to the end of 2016 (an eight year extension). Eligible organizations can now apply this incentive to SWH and space heating and cooling installations (but not pool heating projects). Meanwhile, states, counties, cities, and utilities are increasingly offering incentives.
The use of solar thermal for facility space heating and cooling applications (which can be installed separately or jointly) remains significantly behind SWH installations. Lack of familiarity (along with the lagging incentives) is often seen as leading reasons for this.
About space heating, Guiney says, “New technologies are being commercialized that will allow the industry to do more low cost preheating. And new higher temperature solar thermal collectors will allow us to integrate solar thermal into existing [facility] applications. Some of the new non-tracking solar technologies are operating at temperatures above 200°F to close to 3600°F. This provides more than adequate energy for direct space heating and solar cooling.”
Solar cooling has vast potential—taking into account the air conditioning demand of buildings. Guiney, whose company recently installed a 40 ton cooling project at Fort Bliss, TX, says, “Instead of using waste heat, natural gas, or electricity, [the facility uses] the sun to generate the energy to drive its chiller.” He observes that once these types of systems demonstrate their reliability, there will be wider acceptance.
Solar thermal can serve several areas of facility operations. And as fms look at alternative energy sources, this heat capturing approach may be just the right fit for many sites.
Send your questions about solar thermal to firstname.lastname@example.org.