How Wood Chip CHP Systems are Boosting Energy Efficiency

As businesses strive towards a more sustainable future, new technologies are arriving to meet the challenge. One of these is combined heat and power (or CHP) systems, which are highly efficient processes that capture and use the heat that is a by-product of the electricity generation process. 

Critically, CHP systems are highly efficient, often operating at over 80% efficiency, compared to 30-50% for other typical technologies. This efficiency allows CHP systems to reduce carbon emissions and operating costs and improve energy efficiency.

What Is Combined Heat and Power (CHP)?

Combined Heat and Power simultaneously generate both electricity and useful heat from a single energy source. This efficiency captures heat that would otherwise be wasted in conventional power generation and repurposes it for heating applications.

CHP systems use various fuels, such as natural gas, coal, oil, and biomass. The basic principle involves burning fuel in a gas turbine or an engine. This generates mechanical power, which is then converted into electricity. The excess heat from this combustion process is captured and used for heating purposes, such as warming buildings, producing hot water, or providing heat for industrial processes. This dual production significantly improves overall energy efficiency. Biomass CHP refers to using organic materials, like wood chips, agricultural residues or other plant-based materials, as the fuel source for the CHP system. 

How Does a Wood Chip CHP System Work?

Wood chips are prepared by chipping logs or waste wood into small, uniform pieces. They are then dried to reduce their moisture content, which improves their combustion efficiency.

The dried wood chips are fed into a combustion chamber, where they are ignited using hot air. The heat generated from the combustion process produces steam or hot water.

In some systems, wood chips are gasified before combustion. This involves heating the wood chips in a low-oxygen environment to produce a combustible gas called wood gas, which is cleaned and cooled before being used in a gas engine or turbine.

The heat generated from combustion or gasification is transferred to a heat recovery system. This captures heat to produce hot water or steam, which can be used for heating, hot water supply or industrial processes.

The heat from combustion or gasification can also power generators to produce electricity. In a gas engine-based system, the wood gas powers an internal combustion engine connected to an electrical generator. In a gas turbine-based system, the hot gas spins a turbine connected to a generator.

Larger CHP installations use more powerful equipment, such as gas turbines, reciprocating engines, or steam turbines. These systems are often used in industrial facilities, district heating networks, or large commercial buildings. 

CHP systems aren’t only for large-scale industrial settings, though. Micro CHP systems are smaller-scale installations suitable for individual homes or small buildings. They typically use internal combustion or Stirling engines to generate electricity and heat. These systems are compact and can replace conventional boilers while providing additional electricity.

Benefits of Wood Chip CHP Systems

There are certainly benefits to using a Wood Chip CHP system: 

• Renewability: Biomass is a renewable energy source that can be replenished.

• Carbon Neutrality: The Carbon Dioxide released during biomass combustion is offset by the CO2 absorbed during the biomass's growth, thereby reducing net greenhouse gas emissions.

• Waste Reduction: Biomass CHP can utilise waste materials, reducing landfill usage and waste disposal issues. This will make your business more operationally efficient and yield consistent heat and power production. 

• Energy Security: CHP systems can help diversify your energy supply, reduce dependence on fossil fuels, and enhance energy security.

Challenges and Considerations of Wood Chip CHP Systems

CHP systems offer many advantages, but they also come with certain challenges and considerations that you should take into account when evaluating their suitability. 

One of the biggest considerations that you should take into account is cost. Installing a wood chip CHP system can be expensive. The initial capital investment is higher than that for conventional heating systems due to the cost of the equipment, installation, and necessary infrastructure modifications. Smaller-scale installations may struggle to justify the expense without significant subsidies or long-term financial incentives.

You’ll also need to consider logistical matters. Ensuring a consistent and reliable supply of wood chips can be challenging. This involves establishing a supply chain that includes sourcing, processing, storing, and transporting the wood chips. Variability in the quality and moisture content of the biomass can also affect system efficiency and performance.

The logistical issues don’t end there, either. Wood chip CHP systems often require more space than traditional heating systems due to the need for fuel storage, handling equipment, and the CHP unit itself. Adequate space must be allocated for these components, which may be a limitation for some businesses.

Regular maintenance is essential for the optimal performance of wood chip CHP systems. This includes cleaning ash deposits, monitoring and adjusting combustion settings, and ensuring the mechanical components function correctly. Regular maintenance can be time-consuming and may require specialised skills or services, which can increase operational costs.

You’ll also have environmental issues to consider. While biomass is considered a renewable energy source, burning wood chips can still produce emissions such as particulate matter and volatile organic compounds. Implementing effective emissions control measures is necessary to comply with environmental regulations and minimise the impact on air quality.

The economic viability of wood chip CHP systems depends on several factors, including the cost of biomass fuel, electricity prices, and available incentives. Any of these factors can affect the system's overall profitability and feasibility.

CHP System Applications in the UK

CHP is gaining traction across the UK's industrial, commercial, and residential sectors. In the industrial sector, CHP systems reduce primary fuel use. Latest figures show there are already more than 2,000 CHP plants in the UK, with a combined maximum electricity generation of almost 20,000 GWh per annum, enough to power more than 4.8 million average UK households. Those plants also generate heat - enough yearly to warm 3.8 million average UK households (around 14% of the UK total).

CHP systems are installed in hotels, supermarkets, office buildings, sports centres, hospitals, and data centres. These systems provide energy independence and security, with internal combustion engine CHPs being the most common. The residential sector is also seeing growth in CHP adoption, particularly in district heating systems.

The UK government supports CHP adoption through various incentives and initiatives. The CHP Focus programme provides information, education, and online tools to assist developers. The CHP Quality Assurance (CHPQA) programme also certifies schemes eligible for incentives, promoting high-quality CHP installations. 

Future of CHP Technology

CHP technology is promising, with several trends shaping its development. Biomass CHP systems are gaining traction due to their ability to utilise organic materials, reducing reliance on fossil fuels, and advances in micro CHP units for homes, which are making decentralised energy generation more accessible. 

CHP also plays a crucial role in the transition to sustainable energy by maximising energy efficiency and reducing emissions. It supports the integration of renewable energy sources, such as solar and wind, into microgrids, increasing on-site reliability and resilience. CHP systems can provide essential grid support services, including frequency response and voltage control as the grid evolves.

As we’ve seen, transitioning to a CHP system doesn’t come without its challenges, but the benefits can be enormous. Whether you’re looking to boost your energy efficiency and sustainability or reduce your energy consumption and costs, you might find that this is an investment that could bring considerable rewards to your business.