Combined heat and power (CHP), also known as cogeneration, is the concurrent production of electricity or mechanical power and useful thermal energy from a single source of primary energy. With a CHP system, heat that would normally be wasted in conventional power generation is recovered to meet thermal demands such as space heating, air conditioning, domestic hot water, industrial processes, absorption refrigeration, and desalination.
What is CHP?
Combined Heat And Power (CHP) systems capture heat energy that would otherwise be wasted in conventional power generation. They generate electricity and capture the heat that is byproduct of electricity production to be used in heating applications. This dual use of fuel supplies both power and thermal energy needs from a single energy source, such as natural gas, biomass, coal, or oil. CHP is more energy efficient than separate thermal and electrical supply systems.
How does Combined Heat And Power (CHP) work?
A CHP plant requires a prime mover or engine/turbine which, when fuelled, produces both heat and electricity simultaneously. The most common types of prime movers used in CHP systems include:
– Reciprocating engines – The most widely used prime mover for CHP applications up to around 10 megawatts (MW) thermal input. Engines can run on natural gas, biomass, liquid petroleum gas and other fuels. Applications include commercial buildings, district energy systems and industrial processes.
– Gas turbines – Most suitable for larger-scale CHP over 10 MW thermal input. They typically achieve high electrical efficiency of 30-40% but also require high-grade exhaust to achieve good overall efficiency. Fuelled predominantly by natural gas and liquid fuels.
– Steam turbines – Driven by hot water or steam from either a gas boiler or other combustion source such as biomass. Mainly suitable for industrial CHP and district energy systems.
– Fuel cells – An emerging technology with high electrical efficiencies. Fuel cells produce direct current electricity from an electrochemical reaction involving hydrogen and oxygen. Commonly fuelled using natural gas.
The heat recovered from the CHP process can be used to generate hot water, steam or thermo-electric cooling through an absorption chiller. This recovered useful thermal energy is distributed via piping networks to meet various heating and cooling needs on-site or in adjacent buildings and districts.
Benefits of Combined Heat And Power (CHP)
CHP systems provide a number of attractive benefits compared to conventional separate heat and power:
– Fuel efficiency – CHP can achieve overall fuel efficiencies of up to 80-90% compared to 45-60% for conventional generation. This substantial reduction in energy losses results in lower carbon emissions and fuel costs.
– Reduced carbon footprint – Improving fuel efficiency and reducing primary energy usage significantly cuts carbon dioxide and other greenhouse gas emissions. Some CHP technologies like fuel cells also emit near-zero local air pollutants.
– Reliability – On-site power generation provides higher security and reliability of thermal and electrical supply compared to grid-only supply during outages or emergencies. Critical facilities such as hospitals commonly employ CHP for back-up power.
– Cost savings – Lower fuel and maintenance costs from greater efficiency coupled with avoided investment in new centralized power plants can offer attractive payback periods of 3-5 years or less for CHP projects.
– Thermal load optimization – Captured thermal energy is tailored to specific heating and cooling needs on-site rather than being electrically generated using less efficient resistance heating.
Applications of Combined Heat And Power (CHP)
CHP technology delivers substantial energy and economic benefits across a diverse range of commercial, institutional and industrial applications:
– Commercial buildings – Hotels, hospitals, nursing homes, universities, shopping malls, and other large facilities using both power and heating. District energy also makes CHP viable for multiple buildings.
– Industrial facilities – Food processing, chemical plants, refineries, pulp/paper mills, and other process-intensive industries having thermal and electrical loads. Often co-located with steam hosts.
– Infrastructure – Water/wastewater treatment plants, district heating/cooling systems, and other networked thermal services benefitting from CHP’s higher efficiency.
– Institutional facilities – Military bases, courthouses, prisons and other public sector buildings are well-suited to CHP’s resilience and efficiency advantages.
– Data centers – Rapidly growing energy users that typically rely on inefficient diesel generators for back-up power but can better employ CHP for primary power needs.
Overcoming Barriers and Ensuring Growth
While CHP delivers impressive operational and environmental benefits, high initial capital costs relative to conventional options remain a barrier that many potential customers are not able to absorb. Lack of customer awareness about CHP technology and its full economic case is also an obstacle. To overcome these barriers and realize the untapped potential of CHP, supportive public policies are needed such as:
– Rebates and tax incentives to lower installation costs and achieve parity with grid power, especially for first mover projects that demonstrate CHP viability.
– Streamlined permitting for CHP projects to reduce delays and simplify connecting to local grids and distribution networks.
– Thermal and electric capacity market reforms recognizing the dual value of CHP in meeting both power and thermal needs.
– Mandates or performance standards for new highly energy intensive buildings and industrial facilities to install a minimum level of on-site CHP ordistrict energy.
– Education programs raising awareness of combined heat and power (CHP)technology and case studies among building owners, architects/engineers and local governments.
With the right policy framework and customer awareness, CHP can substantially advance the transition to more sustainable, optimized and resilient energy systems to power economic growth in cities and energy-intensive industries. Long-term these dynamics would support a gradual expansion
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