Robur Gas-Fired Heat Pumps - Advantages

Background     Advantages     Product Spec     Sales & Technical     References

Why Robur heat pumps?
Robur heat pumps are ideal for any commercial or industrial heating application, but show major benefits for organizations and companies where there are one or more of the following concerns :

Carbon Footprint
Despite their excellent local operating efficiencies, all electric heat pumps contribute to global warming on two fronts, directly through the gradual leakage of greenhouse gas refrigerants (HFCs) from the plant and indirectly through the CO2 emissions resulting from the use of fossil fuels burned to generate the electricity required to operate the device.

Estimates attribute 13% of ALL of the world’s Global Warming to released or leaked refrigerants in the atmosphere. This issue is completely eliminated by using a Robur Heat Pump as the natural ammonia/water “pair” has no environmental impact whatsoever.

As well has having an ozone depletion potential of zero, Ammonia has a global warming potential of zero with an atmospheric life cycle of less than a week. In addition, the factory sealed refrigerant system of the Robur Heat Pump means that the opportunities for refrigerant leakage are much less than those of a conventional electric HFC based system.

The direct use of gas at the point of source means that the CO2 emissions associated with the use of Robur Heat Pumps will be much lower than those of equivalent alternatives when operating, power generation and transmission efficiencies are taken into account.

For Example :
A Robur GAHP-A Air Source Heat Pump:
36.2kW of heating. Operating for 60 hours per week / 6 months per year.

Robur Gas Heat Pump
= 1560 (hrs) x 25.7 (kW gas) x 0.19* (kgCO2/kWh gas)
= 7.6 Tonnes of CO2 per year

Gas-Fired Condensing Boiler (with a seasonal operating efficiency of 90%)
= 1560 (hrs) x 40 (kW gas) x 0.19* (kgCO2/kWh gas)
= 11.9 Tonnes of CO2 per year

Electric Air Source Heat Pump (seasonal operating COP of 2.25)
= 1560 (hrs) x 16 (kW electricity) x 0.43* (kgCO2/kWh elec)
= 10.7 Tonnes of CO2 per year

This shows typically that an Air Source Robur Heat Pump can produce Carbon Savings of

* CO2 emission figures for different energy sources are taken from Guidelines to DEFRA’a GHG conversion factors for company reporting, 2007.

Please contact Shorts for advice on and assistance with calculating Carbon Footprint, Total Equivalent Warming Impact (TEWI) and Life Cycle Climate Performance (LCCP) indicators.

Running Costs
Environmental benefits of any plant invariably go hand in hand with improved efficiency and reduced running costs. Robur heat pumps are no different.
The amount of running cost savings from using Robur Heat Pumps over and above equivalent electrically powered machines depends very much on the individual installation’s utility tariffs and running hours. However, in most instances where there is a heating requirement there should be running cost savings over both conventional gas-fired boiler systems and electric heat pump systems of between 30 and 40%.

Equipment Reliability
As the Robur absorption cycle uses a factory sealed refrigerant circuit with no compressor, it’s general mechanical reliability is excellent and the scope for refrigerant loss is minimised.

In the rare event of a refrigerant leak, unlike the odourless HFC refrigerants, the very smallest escape of Ammonia (well below any safety levels) is detectable through its characteristic odour. This is complimented by the fact that most of the Robur units are installed outside and ammonia is 1.7 times lighter than air, so any small leak quickly disperses into the atmosphere. Ammonia is difficult to ignite and exhibits a very narrow range of flammability (under very high concentrations and limited conditions).

In addition, the modular system approach to meeting heating loads means that the building is not solely dependent on one piece of plant and general wear and tear can be spread throughout the system by alternating “lead” units.
Robur’s integral control system monitors specific parameters and warns of factors that may lead to problems in the future, such as blocked air coil or reduced water flow rates etc

Specification Considerations
Although they are capable of producing considerable CO2 savings compared with gas-fired boilers, electric heat pumps have some operational issues that have limited their more widespread acceptance in the UK. These “negatives” can be avoided by using Robur Heat Pumps.

Air Source Heat Pumps
Due to their thermodynamic nature, the operating capacity and efficiency of any air source heat pump are strictly linked to the external air temperature. As the air temperature gets lower, the output capacity from the heat pump reduces and it’s operating efficiency decreases.

If an electric air source heat pump is sized to meet 100% of the building heating requirement at 6°C ambient temperature (an average UK winter temperature) then at -5°C its heat output typically drops to between 60-70% of its full load capacity rendering it unable to meet the building’s increased heating requirement.

In practice, this shortfall in output is addressed by adding less efficient supplementary (normally electric resistance) heating to compensate, thereby reducing the overall “system” efficiency considerably.

To make matters worse, the thermodynamics of air source electric heat pumps mean that the operating efficiency (COP) ALSO decreases with decreasing external temperature, further worsening the already reduced “system” efficiency.

This is the reason why the seasonal operating COP of an electric heat pump is much more important than the single point design COP when considering resultant CO2 and running cost savings calculations.

Ideally we need a highly efficient heat pump that produces close to full capacity at low ambient temperatures and maintains good efficiencies over the full range of ambient conditions.....
The Robur Air Source Heat Pump, on the other hand, produces almost 100% of its heat output at -5°C ambient temperature and operates with a heating efficiency of 100% even at outdoor temperatures of -20°C

Ground Source Heat Pumps
Electric ground source heat pumps have increased in popularity of late as the more constant temperature heat source of the ground overcomes the negative effects of low ambient temperatures described above.

One of the biggest barriers to the more widespread acceptance of ground source heat pumps at present is the initial capital cost of the ground source heat exchanger required to interface with the heat pump.

This issue is less of a concern when a Robur Ground Source Heat Pump is used as the thermodynamics of the absorption system work in such a way that the amount of heat removed from the ground is almost half that required by an electric heat pump to produce the same amount of heating to the building. A typical electric heat pump producing 35kW of heating requires over 26kW of heat from the ground source whereas the Robur equivalent requires only 13.5kW from the ground. This has a major beneficial effect on the capital outlay for the additional heat exchanger.