Optimising efficiency with CHP

Combined heat and power (CHP) is becoming a popular choice for public sector organisations looking to reduce their building’s energy costs and carbon footprint. Mike Hefford, Remeha CHP’s General Manager, looks at how energy managers can maximise the benefits of this low carbon technology

The extreme cold weather at the start of the year raised important questions on national energy security, highlighting the need both for improved energy efficiency and a broad mix of energy sources. A subsequent spike in energy prices provided an additional economic driver for using energy as efficiently as possible.

Little wonder, then, that buildings with a high requirement for heating and power are increasingly looking to Combined Heat and Power (CHP) as a strategic solution for significant long-term financial savings.

What is CHP?

CHP is effectively a micro power station, but more than twice as efficient. By generating heat and power in a single process at the point of use, CHP is around 30% more efficient than traditional heating plant and electricity supplied solely from the grid.

Instead of rejecting the ‘waste’ heat to atmosphere like traditional power stations, the heat generated by CHP can be re-used in the heating/hot water systems. And by generating electricity on site, businesses can produce electricity at lower gas prices.

In this way, CHP helps organisations meet the energy efficiency requirements of Part L of Building Regulations while providing impressive cost, carbon, competitiveness and energy resilience benefits.

So how can energy managers ensure that CHP installations deliver maximum performance and benefits in their buildings?

4,000 operating hours

The first step is to check that the technology is right for the building. CHP will only operate efficiently and generate cost savings if it is running constantly and at full output – so check that the demand is there.

As a general rule of thumb, 4,000 operating hours is usually the minimum requirement to achieve an acceptable return on investment from CHP – which in our experience can be less than five years. Carrying out a feasibility study will help profile the demand, as will analysing the gas and electrical energy usage in existing buildings. Good suppliers will be able to advise and help with these requirements.

Get the sizing right

Accurate sizing of CHP is essential to minimise the total costs of energy supply for the site – but as each building has unique requirements, there’s no ‘one-size-fits-all solution’. Get the sizing right and a continuously-running CHP unit will generate low cost, low carbon electricity as a by-product of producing base load heating.

Oversizing the CHP will cause the unit to shut down during periods of low thermal demand, resulting in frequent stop/start cycling. To avoid this, the best approach is generally to match CHP heat output to the building base load, with condensing boilers operating alongside to meet peak heat demand.

Again, suppliers will be able to provide valuable technical support, so tap into their expert knowledge from the outset.

Integration and efficiency

The hydraulic design should aim to achieve the highest possible efficiency from each gas-fired component connected to the system. When integrating CHP with condensing boilers, it is key that the boilers operate without influence from the CHP unit.

Condensing boilers operate most efficiently at low return temperatures. So while the location of the hydraulic connection is not an issue with non-condensing boilers, higher return temperatures will adversely affect the seasonal efficiency of condensing boilers.

Even if the return temperature is just 10°C lower, this would increase boiler efficiency by around 4.5%. For a 500kW input boiler running for 4000 hours a year at 3.9p per kWh, this would equate to an annual saving of £986.05 – or £14,790.81 over a 15-year life time.

So how to achieve this? Look to configure the system so that the CHP flow is connected to the common flow pipework, with the CHP return connected to the lowest return temperature to guarantee the longest possible running hours from the system. This will increase seasonal boiler efficiency without any negative impact on the performance of the CHP.

Optimising operational life

80% of the lifetime costs of a building are embedded in the operational phase, so energy managers would be advised to put in place a long-term CHP maintenance contract. This support service also alerts both users and the service team when a CHP service is due, helping guarantee optimum performance and operational life.

Some CHP suppliers offer remote monitoring or visualisation of CHP units. Remeha’s R-GEN CHP units, for example, are supplied with a gateway as standard. However, a DSL (Broadband) connection is required via Ethernet connection to visualise the CHP unit. With an estimated 85% of reported CHP faults able to be corrected and reset remotely, visualisation is a useful tool that can help reduce downtime, inconvenience and unnecessary costs.

For this reason, it’s advisable to discuss visualisation at the early stages to enable faults to be corrected, predicted or even avoided.

Realising the benefits

CHP can bring many advantages to organisations, helping weather energy price fluctuations, improve energy efficiency and manage costs. But the success of this technology inevitably comes down to system design, operation and maintenance. With experienced suppliers able to support on the sizing, integration and maintenance aspects of CHP, energy managers can be assured that the full potential benefits will be achieved.

Mike Hefford, Remeha CHP’s General Manager, heads up a dedicated team of CHP specialists who provide support at every stage of the project. Remeha’s CHP range spans 5.5kWe to 100kWe. To arrange a Remeha CPD on CHP, contact info@remeha.co.uk