Pumped storage plants are finding their niche in the power market. Not only do they generate electricity, but they also produce it at the required level of quality to stabilise the grid and they can also be used to provide extra power at peak times.

In China, pumped storage projects are increasingly in demand for precisely these reasons. The country is rapidly expanding economically and the development of power generation resources to match is lagging behind.

alstom has been working in China for over 20 years and is a company experienced in all kinds of hydro projects, including pumped storage. It also has a joint venture hydro factory in China, and the combination of these factors has contributed to it winning several pumped storage contracts in the country in recent years.

Just recently it signed a contract for the Heimifeng pumped storage project in Hunan province in southern China. The Heimifeng plant, owned by Wuling Electric Power, will be composed of four 300MW reversible pump-turbine/motor-generator units. It is the first pumped storage scheme in Hunan province, and when completed, the plant will play an important role in providing base and peak-load power and greatly ease the power shortage in the province. As sub-contractor to Dongfang Electrical Machinery Co, Alstom will supply, erect and commission one complete unit and provide components for the other three units, as well as technical support.

History

As recently as the late 1990s, China was experiencing a serious oversupply of electricity. This oversupply was the result of the closure of a number of state-owned industrial units, which led to a significant reduction in electricity demand from parts of the industrial sector. In response to this reduced demand, the Chinese government closed a number of small thermal power plants and imposed a moratorium until January 2002 on the majority of new power plant construction projects.

In the light of subsequent economic growth, which exceeded predictions, this reduction in generation capacity proved to be an overcorrection. Consequently, the surge in electrical demand has now outstripped the construction of new generating capacity, despite the approval of dozens of major new power plants since 2003. The long construction lead times for such projects simply haven’t been able to keep pace with demand – which is increasing at around 15% per annum.

By the end of 2004, China was experiencing a shortfall in generating capacity of around 30GW. Over 120GW of generating capacity is currently under construction and it is anticipated that supply will have caught up with demand by 2007.

As with any extensive power infrastructure, however, managing the grid to cope with fluctuations in demand presents a major challenge. In response to this challenge, the Chinese authorities have identified pumped storage as one of the most effective measures for improving the quality and reliability of the power grid. Pumped storage not only has the capacity to optimise the systematic structure of the power supply, it also enhances the management of peak demand and response to emergencies.

Clearly, a basic requirement for any pumped storage project is two reservoirs separated by a sufficient gradient that water running from the higher reservoir to the lower reservoir will have sufficient velocity to turn the turbines and generate electricity. As there are only a few natural sites that meet these criteria, such reservoirs are usually constructed.

Within China there are essentially two types of project. Domestic projects are still restricted to using local companies, but with higher technology projects, such as pumped storage projects, it is common practice to have foreign companies involved – as long as they satisfy certain criteria.

One important consideration has always been that the overseas company should have a good working relationship with a local manufacturer. References are also important, as the Chinese want to make use of the latest technologies. Decisions are based mainly on technical and economic considerations. As a result, factors such as energy efficiency and life cycle costing have now risen to the top of the agenda.

Cooperation with local partners

The performance of the equipment used on major projects is now a key consideration and it is often this requirement that leads to the involvement of overseas companies that can supply world-class products. And while China’s local manufacturing skills continue to improve there are many situations where foreign expertise is beneficial.

In such cases, the foreign company may work in partnership with a Chinese company or as a sub-contractor to that local company. This was the case when Alstom was awarded the Heimifeng contract. After some initial training both parties will work together on design, drawings and manufacturing.

There is involvement from Chinese companies right from the start and as the project proceeds they gain a good understanding of the equipment being used. As a result, they are able to undertake routine maintenance following completion of the project. In addition, while the Chinese companies may not have the resources to carry out major repairs, they do have the knowledge to analyse the causes of faults and identify the remedial action required.

The Chinese insistence on localisation is nothing new. In recent years, localisation has also been seen as a way of reducing the overall costs of the project through the use of lower cost local manufacturing. This approach also has a beneficial impact on the Chinese economy, by increasing the revenue of indigenous manufacturing companies.

As well as being able to provide the necessary quality of equipment, companies that are partnering with Chinese firms can also bring other skills to the table and share them with their partners. Experience with all types of equipment to be used on the project is clearly important as it ensures a good understanding of the project as a whole. For a pumped storage project, this knowledge would primarily encompass hydro-generators, turbines and control systems.

Similarly, it is important to have the skills that will be needed to see the project to fruition. Strong skills in mechanical, electrical and hydro design, manufacturing, quality control, testing and project management are all essential elements in a turnkey project.

The Heimifeng project

The Heimifeng project, located in Wangcheng county, Changsha City, is close to the electric net load centre of the Chang-Zhu-Tan region of Hunan province. The power station is only 25km from the urban Changsha area; hence, the geographic location is very good, and accessibility is very convenient.

The gross water head/static pump head of the project is 335/273m. Four reversible units, each with an installed capacity of 300MW, will be installed in the underground power house. After completion, the power plant will be connected to a shaping substation of Hunan’s electricity grid by one 500kV and two outgoing circuits. The transmission distance is 15km.

The power plant is a daily adjustable pure pump storage station. After completion, the power station will undertake such tasks as peak regulation, valley filling, frequency regulation, condensing and emergency stand-by in the Hunan and Huazhong electricity grid.

Alstom equipment will be manufactured in the company’s factories in China, France and Switzerland. The first unit is scheduled for commercial operation at the end of 2008 and the last in the fourth quarter of 2009.

Besides Hemifeng, Alstom’s other pumped storage references in China include Guangzhou I (4 x 306MW), Shahe (2 x 51MW), Zhanghewan (4 x 255MW) Bailianhe (4 x 306MW), Huizou (8 x 306MW) and Baoquan (4 x 306MW).

Construction works

A typical pumped storage project will take around 40 months to complete, comprising a number of key stages, which are illustrated by the Huizhou project. The Huizhou power station is located 100km from Guangzhou city on the Dongjiang river. It has an installed capacity of 24MW, made up of eight units of 3MW each, with an annual electric output of 3.8GWh. The scope of supply covered the design, manufacturing, transport and supervision of building and commissioning of 306MW reversible pump-turbine/motor-generator units, all associated auxiliaries, electrical BOP and control systems. All of this equipment was manufactured in Alstom’s facilities in Brazil, China, France and Switzerland.

The initial civil work for the Huizhou project required the construction of two reservoirs. The upper reservoir, which has a capacity of 20Mm3, comprises a major dam, along with four minor dams. The major dam and the third and fourth minor dams are constructed as reinforced bar concrete panel piled dams, while the first and second minor dams are on a concrete gravity design. The flood spillway is located at the middle brook of the second dam.

The lower reservoir, which also has a capacity of 20Mm3, also consists of a major dam and a minor dam. Both are reinforced bar concrete piled dams.

There are two identical underground power plants with four units each. The equipment provided for the project is listed below:

• 2 x 4 pump turbines – 306MW, 500rpm, with speed governor, auxiliaries and inlet valves.

• 2 x 4 generator motors – 334MVA, excitation, generator/main transformer, protection and auxiliaries.

• Tailwater emergency gates.

• Bridge cranes (machine hall , emergency gallery).

• Cooling, drainage, LP air, HP air and water depressing, oil treatment system, hydraulic measurements.

• 18kV IPB, SFC, GCB, electrical braking, 18kV station service, 10kV station service, 400V distribution switchboards, 500kV cables.

• Control system and protections.

Conclusions

There is a commonly held misconception in many Western countries that Chinese technology projects are based on lower standards of performance and quality than other countries. While this may have been the case 20 years ago, it is certainly not true of modern China.

Largely influenced by its changing role on the international stage, the country has embraced the qualities that would characterise such projects in any other industrialised nation and these are now firmly entrenched as the primary considerations in specifying any technology-based project.


Author Info:

Christian Rambaud is head of pumped storage projects at Alstom