LPG-powered heat VRF system launched

What do you do when a building needs air-conditioning but the site is maxed-out on electrical power and there is no access to a mains gas supply?

This problem can arise at places such as country hotels, golf courses, leisure centres in rural settings, military bases and temporary facilities for sporting events. The situation also occurs surprisingly often in urban areas.

To date, the only option has been an expensive and potentially disruptive upgrade to the power supply. Now an alternative is available, based on a new approach to powering air-conditioning using bulk liquid propane gas (LPG).

This solution is the result of a pioneering partnership between Calor Gas and air-conditioning supplier Oceanair Distribution. The technology uses commercial grade LPG to power a heat pump VRF air-conditioning system. The fuel, more commonly used for heating, is held in storage tanks often seen outside buildings. Any source of LPG fuel produced to BS4250 can be used.

The air-conditioning technology is based on a Sanyo gas heat pump VRF system, while the LPG-powered technology is driven by an internal combustion engine. It operates on the same principles as LPG-powered cars; this is the first time it has been applied to a three-pipe VRF system.

The key technical issue in relation to running a geothermal heat pump on LPG relates to the much higher calorific value of the gas. At the heart of the technology is a modified two-litre Nissan engine, operating at 800-2100rpm. It is equipped with conventional engine components, such as spark plugs, oil and air filter.

The outdoor unit housing the engine requires maintenance every 10,000 running hours – roughly three years of standard use. Maintenance is similar to car servicing: change of oil and air-filter, spark plugs, tightening of the drive belt and so on.

The indoor units are serviced conventionally, as per standard electrically powered air-conditioning units.

The system only requires connection to a single-phase power supply for start-up, controls and the unit’s inverter-driven fans. It only requires a maximum of 7.7Amps of operating current.

The unit’s efficiency ranges from 1.4 (140%) to 1.6 (160%), when used as a heating or cooling system respectively. These figures are based on a 100% load capacity. As with all VRF type products, efficiency improves significantly at part-load conditions.

The system has additional benefits, as it provides “free” hot water plus electricity generation (see figure 1). If both “free” hot water and electricity are utilised, it is possible to deliver efficiencies up to 220%.

As this solution is usually the only option, comparisons of running costs are not key to the decision to specify.

Piped mains gas (natural gas) will always be lower cost than LPG delivered by lorry. But if mains gas is not available, it will nearly always be much cheaper to install a bulk gas tank than to extend the gas main. The technology is an excellent replacement for oil-fired heating systems, against which it is claimed to offer an immediate cost saving.

Calor Gas contains 2.5 times more energy than mains natural gas. In a like-for-like design, the LPG-powered GHP system offers a small running cost saving over an electrically powered system. However, in an ideal application, such as the model above, the cost saving is about 40%.

The system is available in a number of formats and capacities:

• ECO G Power – 20hp

• Three-way ECO G – 16,20,25hp

• Two-way ECO G – 13,16,20,25hp (20hp = 56kW cooling and 63kW heating)

How does the cost of a Calor Gas-powered GHP installation stack up against a traditional natural gas or electric project?

Based on a like-for-like application (say a 20hp installation), if electric equals 100% (£25,000), natural gas version equals 120% (£30,000) and LPG equals 120% (£30,000).

However, where there is insufficient power on site, a typical electrical upgrade would cost about £15,000 and a gas upgrade about £10,000 – whereas an LPG install would cost only £500.

A number of projects are successfully running in the UK. Because of the energy efficiency of the system, enhanced capital allowances are available, covering equipment and installation.