Hospitals often need significant amounts of energy with an elevated minimum load due to the critical functions they support. The work of cooling and heating air and water creates waste heat that usually gets rejected back to the atmosphere. This rejection sends useful energy right out the door with no benefit to the owner who paid for it. Are there ways this heat can be reused? How effective are the solutions? In this article, we will review the options owners and engineers can use to capture waste heat from mechanical and electrical systems, review how climate zones affect the viability of the options, and understand which option fits the project.
Available energy resulting from heating or cooling a building comes from many sources. This article will focus on three types: heat recovery from airstreams, water to water heat exchangers, and combined heat and power (CHP) cogeneration. Each of these methods has varying levels of energy production and savings with cogeneration providing the largest and most direct capture of waste heat for energy savings and campus distribution. In the local California market, heat recovery from airstreams does not typically provide return on investment that is short enough, so it’s not often seen, although some 100% outside air systems with high levels of exhaust should still be considered for a financial evaluation.