The recovery of heat from power generation in Scotland: study

6 Components of Successful Schemes

Recovery of heat from large power stations has not been undertaken in the UK in the recent past. However, from a technical and financial standpoint it is possible and is undertaken elsewhere.

6.1 International Lessons

It is useful to consider some of the experience from countries with significant district heating networks. This is drawn from:

• Experience in Denmark
• Details from the Case Studies

6.1.1 Denmark

Around 60% of domestic consumers in Denmark are heated from district heating systems ^[19] . The growth of district heating started in the 1970's in response to the oil prices shocks. A series of heat laws were passed, which steadily increased the role of district heating. Each version of the Heat Law introduced new features. At the current time the key elements are:

Heat Planning

Denmark passed its first heat supply law in 1979. The law contained regulations on the form and contents of heat planning in Denmark. The heat planning requirements were divided into phases:

• In the first phase, local authorities were to prepare reports on their heat requirements, the heating methods used and the amounts of energy consumed.
• In the second phase they were also asked to assess heat needs and heating possibilities to meet future requirements. This was used to produce regional heat summaries, leading to regional heat plans. The plans were required to show the areas where various forms of heat supply should be prioritised, e.g. district heating or natural gas. The plans also showed where future heat supply systems and pipelines should be located.

Connections

The first law on heat supply gave local authorities the power to oblige new and existing buildings to connect to public supply. Most consumers were obliged to connect to individual natural gas or district heating systems.

A subsequent amendment introduced a ban on installing electric heat in new buildings. This was then extended to include a ban on electric heat installations in existing buildings with water-based central heating systems.

In practice, the ban and obligatory connection made it possible for local authorities to ensure that energy supply companies' earnings were not undermined by an insufficient number of connected consumers, in turn ensuring that investments made were not lost.

Conversion to CHP

The foundations of policy from the 1970's and 1980's was continued in the 1990's with a programme of conversion of district heating schemes to use lower carbon fuels and/or generate electricity as well as heat. The results are shown below, with details of the numbers of CHP and district heating plants in Denmark:

Public-heat supply (cities)

• 16 centralised CHP
• 285 decentralised CHP
• 130 decentralised district heating plants

Private heat supply (enterprises, institutions)

• 380 CHP
• 100 district heating plants

Conclusions

The example of how policy and the market for district heating developed in Denmark show that a long term approach can effect a transformation. The context for the policy in Denmark was a need to move from dependence on imported fossil fuel, prompted by oil price shocks from the 1970's.

The context and policy drivers for district heating in Scotland are different - hence while there are valuable lessons from the Danish example, the results need interpretation and translation into the Scottish context.

A wider range of international experience needs to be examines, the cases studies in the following sections from further insight.

6.2 Case Studies

The following three case studies, one from the UK, one from Germany one from Austria show large scale power stations that supply heat. Important lessons can be learnt from reviewing the policies that contributed to the success of these examples including:

Case Study 1: Isle of Grain LNG terminal

• Under Section 36, power station developers are required to have considered heat loads in the nearby vicinity that could allow the station to be operated as CHP. In the case of Isle of Grain, E. ON worked with the authorities and government advisors to identify heat loads suitable to enable CHP. E. ON subsequently chose to further develop the generating station as a CHP plant rather than a power only generating station.
• As a good quality CHP the scheme electricity output is exempt from Climate Change Levy ( CCL) and therefore Levy Exemption Certificates ( LEC's) can be claimed for electricity generation.
• CHP benefits under the EU Emissions Trading Scheme from increased carbon allocations compared with power only electricity generation. For a CHP plant of this size the benefit would be likely to be in the order of 25-30% more carbon allowances compared with power only. This reduces the number of allowances that will need to be purchased by the generator under the scheme.

Case Study 2: Mellach (nr. Graz), Austria

• Drivers to reduce particulate emissions in area of higher population density.
• Incentives are in place for end users to connect to the district heating system, in the form of grants of between 500-1000 Euros towards the cost of connection (this is funded by regional government body).

Case Study 3: RDK 8, Germany

• Financial incentive-district heating customers are charged a one-off connection charge to connect to; the district heating system and for the hydraulic interface unit (this is currently subsidised by 50% by Stadtwerke-Karlsruhe).
• Renewable Energies Heat Act ( EEWärmeG) (Jan 2009) - German law that introduces the obligation for new buildings to use renewable energy for domestic hot water and space heating. Compliance can include connection to a district heating scheme that has a minimum share of renewable generation or CHP.
• Baden-Württemberg, the Renewable Heat Act ( EWärmeG) (2010) - The region of Baden-Württemberg has its own version of the EEWärmeG, this applies to existing buildings not just new buildings.

6.3 Case Study 1: Isle of Grain LNG terminal

Name: Isle of Grain LNG terminal
Country: England
Power output: 1.3 GWe
Heat output: 340 MWth
Fuels: Natural gas
Core technology: Combined Cycle Gas Turbine ( CCGT)

Background

This £580 million CHP project is currently being developed by E-ON on the Isle of Grain in Kent. The site is an existing oil fired power station which is due to be decommissioned under the Large Combustion Plant Directive ( LCPD) in 2015.

The combined cycle gas turbine ( CCGT) scheme is expected to achieve an overall plant efficiency of circa.72% and will have an electrical generation capacity of 1,275 kWe. The CHP will be able to supply 340 MW of heat to a nearby natural gas terminal.

Heat network and customers

The sole customer of the CHP plant is Grain liquefied natural gas terminal ( LNG), this is owned by National Grid and was the first UKLNG importation terminal. It will have the capacity to meet 20% of Britain's gas demand by winter 2012.

The E-ON CHP plant will have the capacity to supply up to 340 MW of thermal energy to the LNG terminal in the form of (low grade) hot water. It is understood that the heat export is low grade heat recovered from the steam condensation process; this is supplied to the LNG vaporisers at the terminal. The distance of the Grain LNG terminal from the CHP plant is c.2.5 km. The LNG terminal has a sufficiently high heat demand that it will be the only customer of the CHP scheme (the low grade of heat exported would also be likely to be restrictive when considering supplying heat to other customers).

Elements key to the proposal

Drivers

• Reduction in gas consumption at the LNG terminal (required to vaporise the LNG), maximising production and reducing operating costs as a result of reduced fuel consumption.
• The scheme will save 350,000 tonnes of carbon dioxide emissions from the LNG Terminal every year (from the natural gas that will be displaced).
• There will be environmental benefits from the scheme due to a reduction in the amount of heat discharged to the River Medway.
• As a good quality CHP the scheme electricity output is exempt from Climate Change Levy ( CCL) and therefore Levy Exemption Certificates ( LEC's) can be claimed for electricity generation.
• CHP benefits under the EU Emissions Trading Scheme from increased carbon allocations compared with power only electricity generation. For a CHP plant of this size the benefit would be likely to be in the order of 25-30% more carbon allowances compared with power only. This reduces the number of allowances that will need to be purchased by the generator under the scheme.

Barriers

• Cost of district heating connection.

Polices

Under Section 36, power station developers are required to have considered heat loads in the nearby vicinity that could allow the station to be operated as CHP. In the case of Isle of Grain, E. ON worked with the authorities and government advisors to identify heat loads suitable to enable CHP. E. ON subsequently chose to further develop the generating station as a CHP plant rather than a power only generating station.

6.4 Case Study 2: Mellach (nr. Graz), Austria

Name: Mellach
Country: Austria
Power output: 832 MWe
Heat output: 400 MWth
Fuels: Natural Gas
Core technology: Combined Cycle Gas Turbine

Background

The €550m Mellach natural gas fired CCGT CHP plant is currently under construction on the outskirts of Graz in Austria by plant owners Verbund. When operational, the system will have an electrical generation capacity of 832 MWe and also supply 400 MW of heat into the southern part of the Graz district heating system. The overall plant efficiency when fully utilised in CHP mode will be 72.9%. The plant will be installed at site where an existing hard coal power station already provides 230 MW of heat into the district heating scheme.

Heat network and customers

The district heating system will serve the Austria's second largest city, Graz with a population of approximately 270,000. The district heating system is owned and operated by Energie Graz (which is largely owned by public companies), it has over 550 MW of heat load connected to it, includes 4,600 heat transfer stations, 300 km of district heating pipes, 977 GWh/year of energy generation and is served by 4 existing district heating plants:

• The existing district heat plant Mellach (coal) with a maximum possible heat capacity of 230 MW.
• The district heat plant Graz (gas) with an overall heat capacity of 250 MW.
• The district heat plant Werndorf (oil) with a heat capacity of 230 MW.
• The gas turbine power station in Thondorf with a heat capacity of 30 MW.

In addition to this there has been investment in solar thermal which is operated in combination with the district heating system to provide summer hot water demand on the system.

The new CHP plant is co-located with another of Verbund's existing CHP plant which already supplies heat in to southern part of the Graz district heating system and is located circa 20 km from Graz city centre. The maximum heat export from the new Mellach CHP plant is 400 MW and it is anticipated that the CHP scheme will export 800 GWh of heat per annum to the district heating scheme.

The flow temperature is a maximum of 120°C in the winter and at max 70°C in the summer with a return flow temperature of approx. 50 °C.

Elements key to the proposal

Drivers

• Existing district heating infrastructure already in place.
• Drivers to reduce particulate emissions in area of higher population density.

Barriers

• No specific barriers identified.

Polices

• No specific policies have been identified.
• Incentives are in place for end users to connect to the district heating system, in the form of grants of between 500-1000 Euros towards the cost of connection (this is funded by regional government body)

6.5 Case Study 3: RDK 8, Germany

Name: RDK 8
Country: Germany
Power output: 912 MWe
Heat output: 220 MWth
Fuels: Hard coal
Core technology: Ultra-super critical coal (with steam turbine)

Background

The RDK 8 CHP plant in Karlsruhe, will cost c. €1b. This will provide 912 MWe of electrical generation and supply up to 220 MW of heat for district heating. Energie Baden-Württemberg AG (En BW) will own the plant and is developing it on the same site as a number of existing power generators (some of which have now been decommissioned). The CHP plant will be located around 8 km from Karlsruhe city centre. This scheme will utilise an existing pipework connection between the location of the power plants and the municipal district heating system, this is provided by a 4 km (800 DN) pipe which connects to the site of the power plant to the district heating scheme.

Heat network and customers

The power plant (owned by En BW) will provide heat to Stadtwerke-Karlsruhe who operates the municipal district heating system. Stadtwerke-Karlsruhe is largely publicly owned company, shared by Karlsruher Versorgungs-, Verkehrs- und Hafen GmbH ( KVVH) (70%) it also has private investment from En BW (20%) and Thuga AG (10%)

Karlsruhe, has a population of circa 300,000, the district heat network is extensive throughout the city and a significant proportion of buildings in the city are served by the scheme. The district heating network is supplied by a range of different heat sources (and includes a waste to energy plant and heat recovery from the Mi RO oil refinery in Karlsruhe). The maximum heat load that could be supplied from estimates in 2005, were 500 MW.

Heat export from the RDK 8 site, is at 15bar and 130 ^oC, which it the same temperature and pressure as the main heat distribution network. Return water is pumped back to the site at 55 ^oC and 22bar.

District heating customers are charged a one-off connection charge to connect to; the district heating system and for the hydraulic interface unit (this is currently subsidised by 50% by Stadtwerke-Karlsruhe).

Elements key to the proposal

Drivers

• Concerns over long term energy security and estimates from Dena, the German Energy Agency, who predicted a 12 GW shortfall of electricity generation in 2020, unless new non-renewable generation was constructed.
• A financial incentive for using the existing district heating infrastructure that is already in place.

Barriers

• There are limited barriers as the heat network is well established and owned and operated by a separate organisation. The heat is only supplied to the district heating company which reduces commercial risks.
• There were some technical challenges when the initial pipeline to connect the RDK site to the district heating scheme was constructed. These included negotiation around existing structures and the utilisation of a combination of above ground and subterranean pipe work.

Polices

• Renewable Energies Heat Act ( EEWärmeG) (Jan 2009) - German law that introduces the obligation for new buildings to use renewable energy for domestic hot water and space heating. Compliance can include connection to a district heating scheme that has a minimum share of renewable generation or CHP.
• Baden-Württemberg, the Renewable Heat Act ( EWärmeG) (2010) - The region of Baden-Württemberg has its own version of the EEWärmeG, this applies to existing buildings not just new buildings.