Power plant is clean, green and cool

International airport in Changsha has installed an energy-efficient, combined heating and cooling system

Each year, Huanghua International Airport in Changsha, the capital of Hunan province, saves 10 million yuan ($1.45 million; 1.3 million euros; ￡1.14 million) on the cost of air conditioning. It does so by using a cooling system powered by excess heat generated by a natural gas-fired generator, instead of a conventional electric air conditioning system, according to Zhang Xianming, executive managing director of Broad Sustainable Building, a subsidiary of Broad Group, in Changsha.

Zhang says electrical power for the airport is a side product of the heating and cooling system. "Something like 80 percent of the energy for the power plants goes to heating and cooling the building. Most of the time, there will be enough demand for electricity that the exhaust from the generator is enough to power our cooling system."

The system, built by Broad, is part of a combined power plant that provides all of the airport's electrical power, heating, cooling and hot water needs. The US turbine company Cummins made the power plant, while Broad made the cooling system and the Chinese private gas company ENN provides the gas supply.

Liu Guolin, deputy president of Provincial Airport Administration Group of Hunan province, says that according to a case study provided by Cummins, the combined system at Changsha airport will achieve a total energy utilization rate of natural gas of more than 90 percent. "Generally speaking, the energy efficiency of a gas generator is only 40 percent, and the remaining 60 percent is transformed into high-temperature exhaust gas and heat," he says.

Broad's technology is based on absorption cooling, in which a lithium bromide solution is heated to its boiling point, then the solution cools as it condenses. This system is considered inherently more efficient than conventional electric air conditioners, because it eliminates the middle step of generating electricity from heat, then using the electricity to power the air conditioner. According to data from Broad Group, its cooling system uses 30 percent less energy than electric air-conditioners.

In addition, the lithium bromide is more environmentally friendly than the chemicals used in conventionl air conditioners.

A key problem with energy-efficient installations is that they may cost more upfront, even though the life cycle costs may be lower. In many installations, Broad has provided the air-conditioning system at low cost upfront as part of a long-term lease. Then energy savings over the long term are shared between Broad and the site.

"We were the insurer, we were the ones who went to investigate and evaluate if this is a viable project," says Zhang. "We have done hundreds of these and very few had problems.... So it is a very safe investment."

However, the Changsha installation was large-scale and involved gas furnaces made by Cummins. So, in 2011, Broad created a joint venture with ENN, the gas company. Through a consortium of banks, the joint venture sold green bonds to finance the deal. Broad and ENN signed a lease to build and operate the combined heating, cooling and power plant for 30 years. At the end of the contract, the plant will be transferred to the airport for a low price.

This kind of distributed power - in which a large facility, industrial park or neighborhood generates power, heating and cooling locally instead of relying on the national electrical grid - can be more energy-efficient because it makes use of the excess heat that is wasted by large centralized plants that are far from homes or businesses. Zhang estimates that at least 30 percent of the energy from coal goes up the chimney as excess heat.

Another advantage of distributed power systems is that they can be driven by any locally available source of power, including solar, wind, geothermal or natural gas.

A 2011 document issued by the National Development and Reform Commission, the National Energy Administration and the Ministry of Finance set targets to develop five gigawatts of distributed power plants by 2015 and 50 GW by 2020. The NDRC set a goal to create 2,000 decentralized power plants by the end of the 13th Five-Year Plan period in 2020, but only 600 are running now, according to Zhang.

"They are expensive. There are two hurdles: money and equipment. The air conditioners are made by Broad. But the power plants are mostly manufactured by US suppliers, so that is another challenge," says Zhang.

Distributed power plants are part of plan to reform the electrical grid to incorporate wind and solar energy and also to make it more market-oriented. In August last year, the NDRC and NEA established a pilot program creating spot markets for electricity in eight provinces and regions. In addition, in November, they established a pilot program to help owners of distributed power plants to sell their power to neighbors through the grid. According to Cummins, the Changsha airport will receive 5 million yuan each year from such sales of electricity.

Zhang says the leading US air-conditioner manufacturers did not pursue this technology because electricity was cheap and reliable in the United States. However, in the early 1990s, Broad's sales grew by around tenfold each year, because at that time the Chinese electricity infrastructure was very poor. So Broad now has about 80 percent of the worldwide market for this niche technology of absorption cooling.

"A major breakthrough was when we sold a natural gas-powered combined heating, cooling and power plant to the Austin, Texas, department of power, which, at the time, was the world's largest such system," Zhang says. "This was the first time we sold a combined power plant to our clients as a decentralized energy system. It did not use renewable power, but even renewables are not entirely clean. In our calculations, this is the cleanest and most energy-efficient way to use the world's resources."

davidblair@chinadaily.com.cn

(China Daily Africa Weekly 08/17/2018 page8)