Solar collectors

	Model IP01 from China's Haining Yijia has freeze-resistant tubes and a capacity of 240L.

Releases from China and India have well-insulated heat pipes, temperature-protection valves and 0.5mm-thick stainless steel tanks.

The growing popularity of "green" homes and business establishments has led suppliers of solar water heaters in China and India to beef up their output of high-performance models.

To meet the requirements of energy-conscious buyers in Europe and North America, makers are offering CE- and CCC-certified releases that boast well-insulated storage tanks and quick-absorbing heat collectors. Further, companies are raising their production of units equipped with backup systems for cloudy and rainy days.

In line with this, the keen selection of components such as flat-plate and tube collectors, insulators, and tank materials is critical. Strict and consistent implementation of QC measures is likewise vital in making sure that models are safe even during long periods of operation. Durability tests, and water pressure and temperature analyses, in particular, are performed.

In China, both active and passive solar water systems are available. The latter is produced in greater numbers, being less expensive and easier to set up. While passive units are not equipped with circulating pumps and controls, they are said to have a longer service life. The heat collectors, which absorb energy directly from the sun, can be in flat-plate or tube types.

Models from India have solar collectors in thermosiphon-based flat plates or evacuated glass tubes, which are imported mainly from China, Italy or Germany. The pipes can be made of copper insulated with PUF or rock wool.

Recent designs from the country are integrated with safety valves to ensure they can withstand temperatures reaching 300 C. Units are also treated for resistance to corrosion and calcium buildup.

In China, an increasing number of models are fitted with energy-saving vacuum tubes. Some have electric heater-equipped pipes to prevent components from freezing and cracking. These designs are enjoying strong demand in regions experiencing strong winters.

There are also versions with two or more modules, which can be used to supply hot water to hospitals, hotels and other large establishments. Zhejiang Shentai Solar Energy Co. Ltd is among the makers offering such units.

In addition, releases from the company are fitted with an anode magnesium bar stick that prevents buildup of calcium sulphate, silicon dioxide or calcium carbonate. This problem occurs commonly in areas with hard water.

Zhejiang Shentai's typical designs have porcelain enamel inner tanks, 100 to 300L capacity, copper pipes and aluminum alloy exteriors.

At Jiangshan Small Tiger Solar Energy Water Heater Co. Ltd, most models have SUS304 inner and outer reservoirs with a fluorine titanium or zinc-aluminum coating. These feature vacuum tubes and 55mm-thick PU insulation.

According to Duan Minyan, export manager of Haining Xianke Solar Energy Technology Co. Ltd, the Chinese Technical Committees of Standardization will soon require that the thickness of the reservoir tanks be not less than 0.5mm. Currently, most solar water heaters exported from China are between 0.3 and 0.4mm thick.

Suppliers are benefiting from a comprehensive domestic network of raw material providers. Makers claim that the quality of local components is now almost on a par with imported versions. Some companies, however, source materials such SUS304-2B stainless steel, PU, water pumps and expansion tanks overseas on request.

Haining Yijia Solar Energy Industry Co. Ltd procures stainless steel and PU from Italy and Switzerland. The supplier's models boast resistance to freezing and excessive pressure.

All China makers featured in this report are ISO 9001:2000-certified and offer products with CE and CCC approval.

Typical designs from India are safe to use even when operated for 24 hours daily. These have nine to 12 heat-collecting pipes and an output exceeding 50L each day. Temperature ranges from 25 to 70 C. Normally, the cylindrical storage tanks are made of food-grade 304 or 316 stainless steel that can keep water contents safe for cooking and dishwashing.

Among Emmvee Solar Systems Pvt. Ltd's BIS-certified releases is the Solarizer, which has black chrome electroplating over nickel substrate on a 0.2mm-thick copper sheet. This composition helps the unit to withstand temperatures above 300 C safely. The product is constructed from corrosion-resistant steel and copper absorbers to guarantee that water remains uncontaminated. It works properly up to 330 days each year.

In addition, some models from the company are equipped with pressurized systems. These can pump cold water into the tank when the stream runs low. During cloudy weather or the rainy season, a backup heater is at work to help increase water temperature. Designs also have anode rods inside the tank to avert corrosion.

To boost efficiency further, releases at Emmvee have a 2sqm heat-exchange area and a 50mm-thick PUF coated tank. The absorber has an NAL-selective coating, which is the same as that used in satellites. To keep the insulation layer from sagging, the inner tank is supported by a stand.

The glass-pipe heat collectors are produced by one of Emmvee's sister companies in Bangalore.

At Tata BP Solar India Ltd, units are incorporated with safety valves to prevent temperatures from reaching hazardous levels. The company has developed the Hot Max model, which boasts three layers of evacuated tubes. The tanks have PUF insulation to maintain the desired water temperature.

The supplier procures steel from Sail and copper from Hindustan, both of which are based in India. Its products comply with BIS requirements.

Sunsoko Bajaj International Pvt. Ltd integrates ventilation pipes at the sides of the solar water heaters to help release steam and prevent excessive hotness.

Maharishi Solar Technology (P) Ltd offers models with single- or double-glazed flat-plate collectors. The company sources all components from a vertically integrated supplier in Uttar Pradesh.

In-house QC measures are critical in the line. Inspectors ensure that the water temperature and pressure levels are safe, and that the tank and frame structures are hardwearing.

At Tata, overhead tanks undergo hydraulic, leakage and pressure analyses. Controls and thermostats are also subjected to a series of tests using specialized instruments.