High efficiency micro trigeneration systems

This work focuses on micro polygeneration research in three areas: prime movers, cooling devices, and novel system integration options. An original analysis of matching prime mover heat sources to thermally-driven devices is presented, and waste heat for eight prime movers used in micro CHP is characterized using a T-Q diagram. “Micro” is roughly defined as 1–50 kW electric, and an emphasis is placed on systems of <5 kW electric. With regard to cooling technologies, the increasing demand for tight control of humidity and ventilation represents distinct opportunities for integrated energy systems. Polygeneration can provide efficient ways to accomplish better comfort, such as by separating sensible and latent cooling loads. The increasing legislation dealing with GWP of refrigerants for vapor compression systems also provides a driving force for thermally-activated cooling. Advances are being made both for vapor compression and thermally-activated cooling cycles, and a review is provided of research in the areas of transcritical cycles, subcooling, adsorption cooling, desiccant dehumidification, and integrated systems. Many new adsorbent working pairs and desiccant dehumidification materials have driving temperatures low enough to utilize heat from reciprocating engine coolant or even a vapor compression condenser. This enables smaller installations to benefit from combined cooling, heating and power; and opens new possibilities for separating sensible and latent cooling to extend the operating range of sorption-based heat pumps and improve solar cooling efficiency.

► This work reviews recent polygeneration research.
► Analysis of waste heat temperatures and amounts reveals polygeneration opportunities.
► Low regeneration temperature heat-activated devices improve efficiency.
► Separating sensible and latent loads is an important opportunity for polygeneration.