Monday, April 28, 2008

CHP... easy as 1-2-3

Well, maybe not that easy. But certainly more suitable to green building techniques than its relative unpopularity would indicate. CHP stands for Combined Heat and Power, also known as cogeneration. It's pretty rad -- heat waste from on-site power generation is captured and reused to help power heating and cooling systems. In short, it's twice as efficient as separate heat and power systems and reduces carbon footprint. Here's a diagram:

The benefits of CHP are severalfold, broken down like this:

• Efficiency – Captured waste heat can be reused for various applications, including heating and cooling and other on-site energy requirements.
• Flexibility – Systems can be adapted to provide various energy delivery services.
• Reliability – On-site control improves energy delivery, self-sufficiency, and security.
• Environmental benefits – Produces lower emissions than conventional separate systems.

My report uses the local Dell Children's Hospital as a case study, which has been instructive because CHP, although cool and all, does have its drawbacks. In addition to high startup costs, CHP installation requires a crapload of advance planning, tight design integration, on-site expertise, and ongoing optimization. On top off that, the CHP system doesn't provide the cost-savings as advertised -- it costs about the same as a conventional power generator would.

Having said that, the net benefits for CHP are positive, provided a building meets a certain profile -- long hours of operation, desire for 24/7 energy reliability/security, coinciding power and thermal loads -- which makes hospitals a good match.

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