What CHP does
Combined Heat and Power (CHP), or cogeneration, produces electricity and useful heat from a single fuel source. Instead of venting engine or turbine exhaust and jacket heat, a CHP plant captures it for space heating, process steam, or domestic hot water – lifting total fuel efficiency from ~40% (grid power alone) to 75-90%.
Where air-to-air recovery fits
CHP handles the high-grade heat loop (water/steam). But buildings paired with CHP still vent conditioned air through ventilation. An air-to-air heat exchanger on the HVAC side captures the remaining low-grade exhaust energy, complementing the CHP water loop.
Typical applications
- Hospitals and campuses with steady year-round thermal demand.
- Industrial sites needing both power and process heat.
- District heating schemes feeding multiple buildings.
Sizing principle
CHP is most economic when the heat demand is continuous and matches the engine’s output. Oversized CHP that dumps heat wastes the advantage. Pair it with waste-heat recovery basics: capture every grade of heat, high to low.
Payback and carbon
With volatile energy prices, well-matched CHP often pays back in 3-6 years and cuts site CO2 by 20-30%. Validate with a payback calculation before committing.
Matching heat grade to use
CHP produces high-grade heat as hot water or steam, which should serve the highest-temperature demands first: space heating distribution, domestic hot water, and any process load. Lower-grade ventilation exhaust is then handled by air-to-air recovery on the HVAC side. Treating heat in grade order, from the CHP loop down to the ventilation air, extracts the most value from every unit of fuel.
Operations and maintenance
A CHP plant is a continuously running engine, so its maintenance schedule and availability matter to the payback. Plan for periodic servicing, monitor engine efficiency, and ensure the heat-demand profile stays matched to output. A unit that frequently trips or dumps heat loses its advantage quickly. Regular reporting of fuel saved versus a grid-only baseline keeps the business case visible.
Layering with building-side recovery
Even with CHP, individual buildings still vent conditioned air. Adding local air-to-air exchangers reduces the ventilation load the CHP must cover and smooths the central plant duty. The two strategies are complementary rather than competing: CHP for high-grade central heat, air-to-air for distributed low-grade exhaust.
Frequently Asked Questions
Does CHP replace air-to-air heat recovery?
No. CHP handles the high-grade water or steam loop, while air-to-air recovery captures the low-grade ventilation exhaust. The two are complementary.
When is CHP most economic?
When heat demand is continuous and matches the engine output. An oversized unit that dumps heat wastes the advantage.
What payback periods are typical for CHP?
Well-matched systems often pay back in 3 to 6 years and cut site CO2 by 20 to 30 percent, but validate with a payback calculation first.
Which buildings suit CHP best?
Hospitals, campuses, and industrial sites with steady thermal demand, plus district heating schemes feeding multiple buildings.