Repowering

Repowering , dt. About plant regeneration , replacing old denotes power plant parts for power generation by new plant parts, for example with a higher efficiency , with parts already existing equipment and infrastructure can be reused. Repowering can also change the type of power plant: for example, a coal-fired power plant can be replaced by a combined cycle power plant . Block 1/2 of the Simmering power plant is a concrete example of repowering and the conversion into a combined cycle plant .

Two advantages of repowering over a new system are the existing permit and the often existing acceptance of many residents. New permits are often the trigger for public protests .

The ideal time for repowering

Power generation systems, like all technical systems, are mostly designed for a specific service life . This is followed either by a thorough overhaul, in which many core components are replaced, or the plant is shut down. When is a good time to repower also depends on other factors:

how much the plant's technology has developed since it was commissioned
how much maintenance the old system is
whether major repairs or maintenance work are pending
how alternative technologies have evolved
whether the investor expects future technological advances
how high the financing costs of a new system are. Investments are more attractive in times of low real interest rates than in times of high real interest rates.
whether you can do without the system during the renovation period
if a system has been destroyed or seriously damaged by an accident
in the case of fossil power plants: how high the fuel costs and their relationship to each other (oil: gas: coal) are and how their future price developments are estimated

When changing the type of power plant, the purpose of the respective power plant (base load, medium load, peak load) must be taken into account. It is also possible to replace nuclear power plants with conventional thermal power plants (and vice versa). When a thermal power plant is replaced by a new thermal power plant, the maximum possible output of the new system depends on the maximum allowable warming of the water and the cooling tower capacity.

Wind energy

Repowering at the same location

Repowering is of great importance in the wind energy industry . Wind turbines are designed for a service life of around 25 years. Due to the rapid development of technology in recent years and greatly reduced electricity generation costs, it is in many cases profitable to replace old, small systems with new, larger ones before the end of their technical life. There is an international market for used systems that focuses in particular on systems that are still being built in this form. Old systems are often used as a spare parts store. In Germany, 116 plants were dismantled in 2010, 170 in 2011, 252 in 2012, 416 in 2013 and 544 in 2014.

In 2018, the Seeoff R&D project was started with the participation of Repowering in order to investigate strategies for dismantling and repowering offshore wind farms.

Benefits of repowering for the general public

New wind turbines run more smoothly, as the maximum speed necessarily decreases with increasing rotor diameter (e.g. from 30–40 / min at nominal power for 500 kW systems to approx. 10–12 / min for 3 MW systems with large rotors)
New wind turbines run quieter (better wing aerodynamics and geometry and structure-borne sound decoupling)
Modern systems are significantly more compatible with the power grid than old ones
New wind turbines generate a significantly higher electricity yield than old wind turbines. In many wind farms, there are significantly fewer turbines than before after repowering, despite the often increased output. The reason for this is the increasing output of wind turbines. In the mid-1990s, many wind turbines that were new at the time had 0.5 MW (= 500 kW); around the year 2000 it was 1 MW, in 2014 the average output of newly installed onshore wind turbines was around 2.7 MW.
Repowering can also be used to correct planning errors from the pioneering years of wind energy use (e.g. insufficient distances to residential developments) or to merge individual locations into wind farms.
When repowering, new requirements and laws (e.g. TA Lärm and new distance rules) must be observed.
In 2012, 9,359 systems in Germany reached an age of 12 or more years. They are mainly located in windy North German coastal locations and offer great potential for repowering. Together they had an output of 6,104 MW (an average of 0.652 MW = 652 kW).

Advantages for the operator

Repowering in action in Hellschen-Herringand-Unterschaar

New wind turbines usually achieve more full-load hours through technical development and changes in the structural design (e.g. greater hub height or a higher rotor area per kW of nominal power) . In the case of double the nominal output, the guideline is usually three times the electricity yield of an old wind turbine.
New wind turbines are more reliable and require less maintenance than old ones.
Anyone who wants to build a wind turbine at a new location that has not yet been used for wind turbines has to wait a long planning process and cannot be sure that the site will ultimately be approved for a wind turbine. Existing locations enjoy grandfathering .
In Germany, the Renewable Energy Sources Act (EEG) granted between August 2004 and July 2014 financial incentives for repowering old wind turbines on land ("onshore"). The EEG 2004 provided for an extension of the increased initial tariff for operators of new wind turbines that replace old ones in the area. The 2009 EEG significantly increased the incentives for repowering: operators received an additional repowering bonus in addition to the initial remuneration of 0.5 cents per kilowatt hour. Since the EEG 2014 came into effect, operators of new repowering systems no longer receive any additional benefits.

Possible problems

It is not always possible to replace existing wind power plants with larger and therefore usually higher plants, for example if no higher plants are permitted due to the risk to air traffic. Larger systems also require more complex foundations, which can greatly increase the costs for repowering measures in unfavorable soil conditions. The delivery of large components can also be time-consuming.