As gas prices increase, air source heat pumps should be on FMs' shopping lists. Steve Allen, of energy efficiency engineering consultant Cavendish Engineers, tells us why UK businesses should ditch the old boiler.
11 August 2014
Stories about fracking and gas reserves have filled the press in recent months. According to government statistics, the UK's natural gas reserves have been in decline since 1994.
Our proved and probable reserves are now estimated at 461 billion cubic metres (bcm), which is a reduction of 32 bcm compared with last year. So, although we may look to fracking and purchasing gas from Russia in the short term, shortage of gas is likely to become a reality. Furthermore, is gas a sustainable option for future generations? Why are we still using it?
Gas is still a preferred option for most organisations in the UK because of its carbon dioxide (CO2) ratio and its price. The C02 ratio on gas is 0.189 kg per kilowatt compared with electricity's 0.484 kg per kilowatt. But as the price of gas has increased by 37 per cent over just three years*, and with the greening of the grid, building managers and FMs will soon be persuaded to look at ways to run their buildings on electricity rather than gas.
Air source heat pumps have been available on the market for more than 10 years. As the technology has been developed, its efficiency has increased and the price has fallen. Initially, many clients' concerns centred on the high capital expenditure; this is no longer the case. European manufacturers have had to develop better technology to meet the emission regulations, addressing both combustion and the high cost of energy taxes in mainland Europe.
I spoke on this technology at a recent conference, and some interesting points were raised. In the UK, designers and clients are risk-averse when it comes to new technology like air source heat pumps (ASHP), ground source heat pumps (GSHP) and photovoltaics (PV). My Italian colleagues will tell you that air source heat pumps, as well as energy reduction technology as a whole, are more widely used in Europe and are the technology of choice. Here, while we may moan, we have one of the best climates in Europe to obtain the best results from an air source heat pump as well as PV.
Plant and equipment
In London, 90 per cent of commercial buildings are more than 15 years old. Plant and equipment installed typically includes four gas boilers and packaged chillers on the roof. Again, typically, these are oversized for the building, include boilers that have dry cycling, step control and are inappropriately set up. The adjacent ageing packaged chiller - with an energy efficiency ratio (EER) of about 2.4 - is also oversized and all this is probably fed from a transformer giving 415V.
Remove all this and place one four-pipe air source heat pump in the space vacated by the chiller and, sized correctly, energy saving of more than 40 per cent will come right out of the box. It means less kit, it's automatic with a lower operating expense - and you have an empty boiler house.
- An evaluation of the primary and secondary circuits, and comparison to first principles will reveal any overcapacity.
- Consider lowering flow and return temperatures.
- You should also consider how much of the year you could operate with 50C flow (binned temperatures).
- Consider the hydraulics of the circuit and how the pump rates can be reduced to match.
- Size the ASHP based on the heat required and when it is needed and NOT peak heat loss.
- Along the way, review control strategies. Are they demand-driven and smart or just time clocks?
- Consider the age of existing plant and existing efficiency, compared with new.
- Consider what can be upgraded/reused to enhance, i.e. variable gas burners.
- Develop a plan of replacement and enhancement, based on seasonal logic.
- Consider by whom and how the maintenance strategies will be implemented (less but smart).
This approach usually shows the benefits to tenants and building owners who appreciate the added greening to the project. Modern methods of maintenance and remote monitoring deliver reliability and energy monitoring linked to smart controls. This ensures that demand-led strategies optimise energy input on an hourly basis.
Using out-of-the-box technology to breathe life into older buildings will result in a better thermal environment for the occupants at lower cost and with less impact on the environment.
A culture change will benefit all concerned in the property industry and is a no-brainer when you are considering plant replacement programmes.
It is large property owners who will lead the way in shaping sustainable policies. While we are pleased to be supporting them in their programmes, other companies need to follow and we are aware that most are concerned with the complexities of such projects.
The future involves tapping into specialist resources and consultants to drive forward energy efficiencies.
*The Guardian - 19 November 2013
Steve Allen, managing director and energy consultant at Cavendish Engineers