Cost, efficiency and sustainability benefits can all be realised by CHP in sites with high constant demand for hot water and power, says Mark Gibbons, Baxi Heating’s CHP National Sales Manager
Few would disagree that this has been a year of enormous uncertainty and upheaval. In the public sector, budgets have been under additional pressure due to a double whammy of COVID-19 related costs and loss of income. For energy managers, the challenge moving forward will be to meet tighter environmental targets while balancing financial concerns.
Obvious as it may sound, one of the simplest ways of cutting bills and emissions is to use less energy. Heat is a natural focus for improvement, with retrofit one of the fastest approaches to achieve the savings in older properties. However, as every building will have its own unique requirements, it’s essential to identify the most appropriate solution that will fit the both the demand and the budget.
In sites with high, constant demand for high grade heat, a technology like Combined Heat and Power (CHP) can offer energy managers an economic solution to more sustainable heat and power and improved energy security.
So how does it work? CHP produces useful heat and electricity at the point of use in a single highly efficient process. Rather than rejecting ‘waste’ heat to atmosphere like traditional power stations, CHP captures it to produce useful thermal energy. This can be re-used either for high grade heating or, increasingly, for cold water pre-heat for domestic hot water production. In this way, it is able to meet a building’s heat demand more efficiently, reducing total primary energy consumption typically by around 30% compared with conventional methods.
Boosting the efficiency savings still further, is CHP’s ability to generate lower carbon on-site electricity at lower gas prices.
The operating cost benefit of CHP will depend on the difference in gas and electricity prices. This is often referred to as the ‘spark gap’ or ‘spark spread’ – the wider the spark spread, the greater the return. With gas prices currently at around a quarter the price of electricity, CHP offers an attractive economic option – one that is capable of delivering payback within three years in a well-designed, well-maintained system.
Further, onsite generation offers energy managers the opportunity to offset fluctuations of wholesale energy prices, ensuring greater energy resilience and control over energy costs.
Low NOx, low CO²
So how ‘green’ is CHP? Classified as a low-carbon technology, most natural gas CHP engines nowadays will emit almost zero CO² due to the set-up of the engine and lambda sensors.
Advanced CHP units are also low NOx. Operating in conjunction with a water heater in a well-designed system, a CHP could reduce NOx emissions by up to 75% compared with a boiler or water heater alone.
Greening the gas
Then there’s the future opportunity to switch to a greener fuel. The feasibility of repurposing the existing gas grid to transport green gas is being explored by ourselves and others to offer a low disruption solution towards decarbonising our older building stock. CHP plants could be adapted or produced to operate on alternatives to natural gas, such as hydrogen and bio-methane, reducing or eliminating carbon emissions at the point of use.
We should consider too applying complementing methods of heat generation, including CHP, in a hybrid system. For example, using lower-cost CHP electricity to power air source heat pumps will multiply the efficiency of the system while neutralising the carbon emissions and reducing electricity costs.
Heat networks, which will play an increasingly important role in the sustainable heating policies mix in dense urban environments, can use a range of heat generation solutions. We envisage a design where hydrogen boilers and CHP units provide high grade heat for domestic hot water provision while powering ASHPs for low grade heat.
Additionally, CHP can be seen as a useful tool in encouraging the widespread adoption of electric vehicles, a move considered by many as key to achieving net-zero carbon emissions. Organisations have the option to use this lower-cost electricity to provide electric vehicle charging points for their customers. Providing access to charging points in council-owned leisure centre car parks, for example, would support the national drive to carbon neutrality while helping bolster their own coffers.
Creating a more sustainable future
As energy managers strive to make their buildings more sustainable, energy efficiency is more important than ever.
Driving down energy consumption and waste in buildings is fundamental to achieving this. Retrofitting CHP offers a real, achievable opportunity to do just that in buildings with high demand for high grade heat in the immediate term, with the opportunity for additional futureproofing. Of course, accurate sizing and a well-considered design are key to achieving the full benefits along with good maintenance and routine servicing. But with early engagement between all stakeholders, and the support of experienced suppliers who can provide technical input and insight, the financial case for CHP in these uncertain times is certainly compelling.