Pumped storage hydro

pumped storare hgydro

Increasing versatility in hydropower

Hydropower is a versatile technology, and there are many ways to utilize water for energy production. Pumped hydro storage enables large-scale energy storage and thus flexibility for other, intermittent renewables. Planning and implemention of pumped storage plants could however prove to be challenging due to financial and environmental considerations.

Europe’s development of renewable energy in the EU is expected to increase by about 520 TWh from 2010 to 2020, an estimated 305-400 TWh from wind power, approximately 100 TWh from solar PV and smaller amounts from bio- and hydropower. A strong continued development is also expected after 2020, with visions of a near 100% renewable energy system in Europe by 2050, according to the EU SET plan. Such large-scale development of unregulated and highly variable power is expected to provide significant challenges to the operation of the power system, and a growing need for power generation that can cover consumption during periods of low wind and sun, so-called balancing power. It will also be necessary to store very large amounts of energy excess production during periods of heavy wind and sun, typically 5 to 10 TWh over periods of up to a week or two, which is a characteristic time scale for wind systems North Sea area.

Since the purpose of the whole re-organization of the power system is to make the transition from fossil fuels to renewable energy, we should also adopt the balancing approach with the power coming from renewable energy sources - such as hydropower. The most promising renewable technology to meet both power and storage requirements for balancing power is the use of pumped reservoir storage. A pumped storage hydropower station must have two reservoirs for the storage of water, an upper and a lower. These should preferably be at a place of great height difference and small horizontal distance between. Construction of the new reservoir will be a significant cost if there are no natural lakes or existing reservoirs that may be used, and often creates a too large and controversial interventions in the natural environment. Here the Norwegian hydropower system has a big advantage because it will be relatively easy and inexpensive to build new pumped storage hydropower stations without the need to build new reservoirs, as would normally be required in the rest of Europe. Balance power can also be produced by expanding output capacity of a hydropower plant, without pumping, by shutting down production and collect water in the reservoir in excess periods, and run extra hard in times of deficit. This is currently being done for example for balancing wind power in Denmark.

Technology status

Today, there are a few pumped storage hydropower plants in Norway, but all of these are designed for seasonal pumping, to allow for inflow during the spring flood period in higher altitude reservoirs, and outflow production in the winter period. In Europe there are about 170 pumping plants with 45.000 MW pumped capacity, mostly aimed at balancing heat production around the clock, and therefore with very little longer term storage capacity. A typical European power plant has a capacity of 200-300 MW and can pump water for

6-12 hours before the reservoir is full. There are specific plans for the construction of another 60 plants with a total capacity of 27.000 MW by 2020

A capacity upgrade to existing power plants requires only one (upper) reservoir, while the power plant should have an outlet to the sea, another reservoir or a large lake so that quick turn on/off does not create unnecessary problems below the outlet. In Norway , we have more than 140 power plants with maximum output of over of 50 MW. Eighty-nine of these were part of a study of the potential for expansion of power production conducted by NVE. The power plants in the analysis have an average life of 3.900 hours and a total installed capacity of 17.000 MW. Doubling this capacity reduces the total operating time with almost 2000 hours and a significantly increases the operational flexibility.

A survey conducted by NVE also shows that there are over 100 reservoir-pairs that may be suitable for the construction of pumped-storage plants, 20 of these have a reservoir capacity in both the upper and lower reservoir of more than 100 million m3. Studies conducted by CEDREN for some of these plants in South Norway show that at least 20.000 MW of new capacity in technical terms can be developed to produce increased power and balancing power- while using only existing reservoirs and storage capacity- of several TWh.

Pumped storage hydro will generate revenue by “magnification” of unregulated power that might otherwise be lost or sold at a low price. The development of 10.000 MW of pumped storage power plants will require investments in the order of 30-50 billion NOK. In addition, investments in power lines and/or cable connections to the continent will need to be taken into account. This creates the basis for significant potential employment both in the planning, development and operation sectors.

Challenges

It is important to see the development of new power and pumped storage plants for balancing power in the context of the overall renovation and upgrading that will be needed in the Norwegian hydropower system in the coming years. Much of this power system was developed in the period from the 1950s up to 1990, and there is an ever increasing need for upgrading and renewal, not only for purely technical reasons but also because of market conditions and because society’s views on environmental regulations are changing. In this context, the need to develop pumped-storage power and construction of pumped-storage plants are only two of several drivers that will influence the development. Research needs for the development of the Norwegian hydropower system can be divided into three categories: technological, market and environmental requirements. Pumped storage hydro is a mature technology, but there are special needs and challenges related to the type of development required for large-scale balance power, with particular emphasis on finding optimal solutions for the construction and operation of large pumped storage power plant with long waterways under widely varying operating. This places special requirements on ensuring stability and opportunity for frequent adjustment without incurring damage to waterways and machinery. Since the biggest cost will be the construction of tunnels and underground spaces, it is important to optimize the planning and operation methods and ensure the necessary capacity and expertise.

The market challenges lies in developing solutions to ensure stable revenues, triggering the investments that are needed, both in pumping power plants and transmission lines. In this context, the long planning and construction time for hydroelectric power plants and transmission lines is a significant challenge. However, the biggest challenges are perhaps environmental and in ensuring social acceptance for such developments . There will be challenges and objections to such a major development for the purpose of balancing production in Europe. The major conflicts are perhaps primarily related to the need for extensive development of new transmission system for power, both on land and sea cables. There will also be more adverse conditions in regulating reservoirs. In such reservoirs, there will be more frequent and greater variation in water levels and studies of the effects of environmental conditions in these reservoirs is therefore an important task.

R&D recommendations:

• Development of a pilot project where an existing or new pumping plant will be equipped so that it can be actively used for research and teaching, studying and optimizing the technical solutions, both for electromechanical equipment and tunnels.

• Development of good environmental design, studies of global and local impacts and benefits. policy recommendations:

• Economic studies on income distribution, taxation, municipality/ landowner added value etc.