Here Comes The Sun
- May 29, 2009
Here in California, there’s a buzz brewing in the construction industry that’s going to have quite a future. As you may know, our state has imposed upon itself a noble goal to reduce greenhouse gas emissions drastically over the next forty years or so. You may also be aware that buildings—their construction and operation–typically account for about forty percent of the GHG produced in the United States. Therefore, those of us who plan and design new buildings and communities are intently interested in figuring out how it will ever be possible to meet the stated goal. The quick answer, of course, is that it won’t be if we continue with business as usual. We’re going to have to look beyond the systems and solutions to which we have grown accustomed, and really try out some new and inventive stuff.
The idea about which I am currently the most excited is not, in fact, particularly new, but it’s been receiving a lot of attention lately, and consequently, something of a makeover. That idea is co-generation, or combined heating and power (CHP), as it is sometimes known. Take it one step further and you have CCHP, or combined cooling, heating, and power. Sometimes this is also called “tri-generation.” At the heart of this system is a central plant that burns fuel to heat water to turn a turbine to produce electricity. (The exhaust is “scrubbed” before being released into the atmosphere.) The excess heat is collected and used to warm domestic water or air. Add absorption chillers to this starter kit, and cooling is provided as well. (Though I must confess right here that it still baffles me how engineers are able to produce chilly air from hot water, but I’m working on it.)
Many college campuses and other institutions already have such systems. They are, in effect, their own small utilities. Because many different buildings are able to function off the central system, there are economies of scale. To make smaller, individual projects or communities work with a CCHP system will require sharing of resources in a way that we have not been accustomed to in private development.
On the other hand, we have already done infill projects, which, for various reasons, used a centralized boiler for domestic hot water, so the idea is not beyond imagining. These boilers have typically been powered by natural gas, which is a relatively efficient process, but it still relies on a non-renewable resource as a fuel source. Some of the bigger, industrial facilities, or even our emergency generators, run on diesel. In the new generation of CCHP, other, more sustainable energy sources are being employed, such as bio-diesel made from used cooking oil, or bio-mass, which is typically produced from industrial or agricultural waste products (think sawdust or perhaps cornstalks.)
Perhaps the most exciting idea I’ve seen recently is solar tri-generation. This works similarly to the other fuel-powered systems, except it relies entirely on a renewable resource—the sun—to make electricity and heat water. (Actually, this is more of a solar “team” generation as I understand it. The hot water for heating and cooling is heated up in little tubes run on the roof; the photovoltaics produce electricity that powers the lights and plugs, but also the condensors and fans required to make the chilled air. But who am I to quibble?)
This is what the future looks like—even modest-sized projects will include their own generation facilities in order to dramatically reduce their energy consumption from the grid, thereby reducing greenhouse gas emissions at the generation source. While the environment will benefit, these systems, while expensive at the outset, will absolutely save owners money over the lifespan of a project.
And who isn’t interested in that?
(Daniel Gehman is principal at Thomas Cox Architects. He can be reached at DanielG@tca-arch.com)