28 Energy Saving Equipment
HE FIRST GREE PV-powered, direct-drive centrifugal chiller to be applied outside China is now being installed at Teheran University, Iran. The final 1160sq m PV array will generate around 233kW to power the 340RT cooling capacity centrifugal machine and is expected to be operational this autumn. The array is being installed in two stages, the first supplying 116kW or half the power requirement, with the remaining 50% being supplied by the grid. After a test period, the performance will be evaluated to assess the cost-benefit of proceeding with the second half of the array. On the VRF air conditioning front, the first Gree PV-powered VRF project outside China has been installed in Malaysia. It includes more than 200 indoor units, cooling offices and manufacturing facilities at Yeh Brothers Wood Works (Malaysia) SDN.
The system is powered by a large array measuring 20,000sqm. Only a third of the power generated is required by the VRF system - the remainder will be used for manufacturing and general office use. It makes complete sense to use the sun’s energy to power air conditioning. As well as being good for the environment, it can dramatically reduce running costs for end users, and has the additional benefit of harnessing a free source of power at the time cooling demand is highest – when the sun is shining.
Over the years, a number of attempts have been made in pursuit of this Holy Grail for cooling buildings. Until recently, however, the expense and relative lack of efficiency of photovoltaic (PV) systems has hampered widespread adoption. However, a development by Chinese manufacturer Gree has opened the way to PV-powered air conditioning as a mainstream technology. It is particularly exciting as it makes possible widespread adoption of PV-powered systems in even relatively high northern latitudes, such as the UK. With cooling capacity measured in MW rather than kW, it brings solar-energy
ACR News August 2015
Klima-Therm aGrees with PV T
powered air conditioning within reach for large or multi-storey buildings with higher cooling demands.
Looking at the number of major buildings planned for construction in London over the next five years, it is easy to appreciate the enormous potential - not to mention the replacement market for aging centrifugal chillers installed in the Seventies and Eighties.
The most obvious benefits are the potentially dramatic reductions in running costs, and commensurate cuts in carbon emissions. Gree unveiled the world’s first PV direct-driven inverter centrifugal chiller over a year ago. With a COP 7.10, it can deliver energy savings of up to 40% compared with a standard centrifugal chiller.
The 2.28MW demonstration plant at the company’s headquarters in China has been attracting attention from a steady stream of visitors. On 17 June 2015, after just 618 days operation, it reclaimed all the investment made in the plant, with 16,110,000kwh of power being generated. From now on, it will save the company more than £90,000 each year. This is reason enough to pay serious attention to PV cooling. However, the benefits don’t stop there. Electricity not used by the chiller can be fed into the grid, helping further to significantly offset capital costs and providing an ongoing source of revenue for the end user.
How it works
The chiller consists of three main components: the photovoltaic system, an inverter-driven centrifugal chiller, and an integrated power control system. Crucially, in the Gree system, DC power generated by the PV is used directly to drive the chiller, under the management of an on-board power control system. This direct PV power approach increases efficiency by between 6-8 %, compared with a conventional grid-connected PV generation plant and air conditioning system.
Gree technology breakthrough opens way to solar-powered air conditioning in UK, as Roberto Mallozzi and Tim Mitchell of Klima-Therm explain.
The system has five operating modes, with varying components of PV power generation and grid energy consumption, which are matched to current demand and solar conditions.
The operating modes are:
■ 100% PV energy powering the chiller; ■ 100% grid energy powering the chiller; ■ 100% of PV energy fed in to the grid; ■ A varying proportion of PV energy powering total chiller demand, with remaining PV energy being fed into the grid;
■ 100% of PV energy being used by the chiller, with the remaining requirement topped up from the grid.
The switch between each mode takes less than 10ms, and is virtually seamless, enabling the system to constantly respond to changes in demand and supply, and select the most efficient mode at any one time to satisfy current cooling needs. With the development of Gree’s direct- drive PV centrifugal chiller, we believe the era of large scale photovoltaic powered air conditioning has arrived. Applications for the technology are numerous, and include large office buildings, data centres, hospitals, schools, shopping centres and the process cooling for industry. Having seen the scale and quality of Gree’s research and development facilities first hand, we have no doubt about the company’s commitment and ability to make the technology available globally, and that it will in due course become a mainstream option.
Gree may not yet be a familiar name in the UK market, but the company manufactures one in three air conditioning units sold in the world today - reflecting growing own-brand sales and its role as an OEM to some of the industry’s leading names. With the arrival of the PV chiller, and a PV-powered VRF system already available, there can be little doubt that it is intent on making a name for itself in the months and years ahead.
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