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Special - Spatial Planning and Energy for Communities in All Landscapes Town and Country Planning Association European Union

Knowledge Pool

Module 4: Implementation of Sustainable Planning

4.2 Power supply

Introduction

One of the main pillars of today’s society is the production and use of electric power which is used for numberless purposes. Electric energy production bases mostly on fossil fuels (oil, gas, coal) and nuclear power. Fossil fuels and nuclear energy dominate the gross power generation mix in EU-27, with a respective share of 51% and 27.4% in 2010. The use of fossil fuels for the production of energy is linked with the generation of climate damaging gases like CO2. CO2 emissions of different fuels in power plans: Lignite = 850–1200 g CO2 kWh, Coal = 750–1100 g CO2 kWh, Gas (combined cycle) = 400–550 g CO2 kWh. But these techniques have also other enormous impacts on the nature/humans like emissions e.g. heavy metals, heating of rivers, mining damages (e.g. mountaintop removal, open pits). Such negative impacts lead to mayor follow-up costs which are often not included in energy prices! The production of energy by use of nuclear sources is also linked with unsolved problems like the storage of nuclear waste and the danger of radioactive emissions (e.g. Chernobyl, Fukushima). Another critical character of both energy sources – fossil and nuclear – is the finiteness of them. However, beside environmental issues also negative economic impacts are a risk for societies in nearer future because of the rise of prices for scarce resources which are used as fuels. Because the world's power demands are expected to rise 60% by 2030. Result of this background is that countries have to transform their energy supply systems anyway in short or long term.

Alternatives to fossil fuel and nuclear power are renewable energies which are already in use in many countries. According to a Eurobarometer survey in 2013 around 70% of the EU citizens think that renewable energy should be the prioritised as an energy option for the next 30 years! Renewable electric energy is generated from natural resources. Renewable energies such as wind power, solar energy, hydropower and biomass can play a major role in tackling the twin challenge of energy security and global warming because they do not deplete and produce less greenhouse-gas emissions than fossil fuels. Renewable energies will become the most important energy source of the 21st century. This needs also a transformation of the energy supply system. Because few major power stations are being replaced by many decentralised generating facilities. Solar, wind, hydro and geothermal power technologies play a key role supplying Europe with clean electricity. The share of electricity generated from renewable sources is in rapid progression. According to the renewable energy statistics done by Eurostat for the year 2010 the portion of renewable in the EU are by 19,7 percent. In 2011, electricity generation from renewable sources, with necessary adjustments for wind power and hydropower, contributed 21.8 % to total EU-28 electricity generation. There is a huge variation between countries in Europe: for Malta the level is negligible (0.1 %), while for Norway it is 104.8 %. In the EU-28, the highest share is recorded in Austria (66.1 %), followed by Sweden (59.6 %). Between 1990 and 2011, total electricity generation from renewables increased by 119 % (Eurostat).

Net integration (see links below for more information): For the integration of decentralised renewable electric energy the grid systems have to be modified to avoid overloads or derating. A “smart grid” uses information and communication technologies for better balancing the power load of the grid as well as the integration of renewables. On the one hand new grids are needed for the integration of renewable energy on local level (local distribution network) and the transport via high voltage networks. Furthermore a smarter net is needed for managing different loads to different times (e.g. for storage).

However, there are many different systems and techniques to produce sustainable electricity. Main systems are:

Relevant parameters to be considered

General Parameters

  • Renewables versus conventional energy (e.g. impact on nature)
  • Landscape versus renewable energies (e.g. landscape or biodiversity change following climate change)
  • Modification of the grid systems
  • Cost-benefit (e.g. repowering)
  • Chances for consolidation of local economy
  • Impacts for citizens/neighbours (e.g. noise or shadow effects from wind farms)

Wind Power:

  • The first requirement when considering the possibility for wind energy is the identification of a suitable site that has a high level of resource.  More specifically it should be windy at the height above the ground at which the rotor will be situated.
  • For large scale onshore and offshore environmental impact assessments (EIA) are needed which can take between 1-2 years depending on the level of baseline data needed by the planning/permitting authority and the sensitivity of the area.
  • Grid connection is needed. The developer needs an agreement / power purchase agreement with the relevant body to ensure distribution and a market for the resulting electricity.
  • Repowering means the installation of a new (bigger) wind turbine by replacement of an older one. The efficiency of newer turbines is much higher “twice the turbine – twelve time more power”.
  • Wind power plants are often linked with problems concerning the dead of birds and bats. But the impact is very low also in comparison to other human activities like buildings, mobility, cats. Bird connected NGO say that the impact of climate change (global warming) is the biggest thread for birds.
  • At offshore wind parks it can generally be observed that the level of acceptance of wind parks offshore is high. When wind turbines are situated some kilometres or ten’s of kilometres offshore there is typically an almost negligible visual effect, in fact many offshore parks will not be visible from shore due to their distance.

Photovoltaic (PV):

  • Identification of a suitable location.
  • Connection or build-up of the grid (not all cases).
  • Ground-mounted solar power plants require land, but their footprint is minimal. Mostly used is former agricultural land, sealed land and conversion land, such as old airports or military fields. After deconstruction of PV the land is still useable for example for farming. On average, a solar park of 1 MW needs 2.5-3.5 hectares of land (EPIA).
  • PV plants can have little impact on biodiversity – the ground partly covered and sealed is usually below 1 %. The German Agency for Renewable Energies summarized studies about the effects on biodiversity in a report, stating that “the existing results show that solar parks can have a positive impact on biological diversity. Although construction projects always involve disturbance of existing flora and fauna, with solar parks there is a chance to improve the quality of habitats for various plant and animal species and even to create new habitats.”
  • PV on roofs have a low local environmental impact and are not very visible (for small applications they are often mounted on the roofs of buildings) typically making public/permitting acceptance high.
  • Grid connected systems require an appropriate licence or permit to export to the grid along with the necessary metering equipment, connected by a professional, to ensure that the level of export to the grid is measured for any subsequent compensation.
  • Larger installations require the appropriate planning permissions.

CHP:

  • Consideration of location of supply facilities to the settlement areas (heat customer), relevant for length of tubes. Costs and transmission lost,
  • Consideration of possibilities to use existing waste heat potentials,
  • Control of the energetic standard of the settlement,
  • Determination of priority areas for the heat supply,
  • Safety of sites/areas for the heat production and routes for the installation of a heat net,
  • Planning determination of facilities for the connection of the heat supply as well as the determination of compulsory connection and usage of a local or long distance heating systems.

Gasification of Biomass (Biogas plants):

  • Bioenergy is considered ‘carbon neutral’ but indirect land use change can negate any greenhouse gas savings from biofuel production based on energy crops.
  • Energy versus land use for food production (plate or tank). In Germany 850 00 ha (5%) of total 17. Mio. ha of land are used for biogas crops.
  • Consideration of noise and odour
  • Depending of the size of the biogas plant the traffic can increase. The feedstock should be a local source. Use of bio waste products from agriculture, industry, municipals is to approve.
  • Connection to the grid.

Combustion of solid biomass:

  • Noise and emissions
  • Depending of the size of the plant the transport.
  • Availableness of the feedstock (e.g. forest residues, wood chips…)
  • Connection to the grid.

Hydropower:

  • Topography is needed for using hydropower.
  • large scale hydropower projects can be controversial because they affect water availability down stream, inundate valuable ecosystems and may require the relocations of populations
  • geologic, social, and environmental factors need to be evaluated
  • When considering a site for hydropower generation it is essential to explore whether the landscape is suitable for dam building and whether the potential output of a scheme is attractive.
  • Large-scale hydroelectric dams are more likely to be involved in environmental issues.
  • Environmental constraints, resettlement impacts, and the availability of sites have limited further growth in many countries.

Geothermal energy:

  • Risk assessment and management for a reliable evaluation of the technical, environ-mental and economic sustainability
  • Social acceptance of geothermal projects by ensuring that potential site and technology specific side effects are typically relatively minor compared to the benefits
  • Considering the structure of the underground
  • The impact of the drilling on the nearby environment. Problems in some regions with earthquakes. Drilling could also lead to surface water pollution (e.g., through blow-outs) and emission of polluting gases into the atmosphere.
  • The pipelines to transport the geothermal fluids will have an impact on the surrounding area.
  • The reduction in the pressure in the aquifers. This could lead to subsidence of the ground in the geothermal facility regions. Re-injection of the condensed and/or cooled water back into the reservoirs could neutralise the subsidence. Re-injection also reduces the risk that the steam is exhausted into the atmosphere or that used water is discharged into surface water.
Planning relevant issues

On spatial planning level (country or regional planning) planers have different possibilities for strengthen / organize /  regulate / steer the development of renewables. The reason why - spatial planning strengthen the energy production via renewables - can be found in climate protection (e.g. greenhouse gases), enhancement of rural areas, recycling of waste materials and the independency of fossil resources. On municipal planning level (land development plan and binding land use plan) planers have different possibilities for strengthen / organize /  regulate development of renewables. Aspects of formal or informal planning:

1. National level
Wind: The town and building code in Germany includes some rules for the repowering of wind turbines.

Wind (offshore): Because of the site specifics (see) the permit for installation of offshore windparks is given by national institutions. In Germany for example by the Federal Maritime and Hydrographic Agency. A planning approval procedure is needed which consist of different steps (national or country level).

2. Country level (e.g. Länder)
Wind: Basis for planning on regional level is the country development plan. In this plans objectives and principles are named for the planning of wind power use. Furthermore specification of criteria’s concerning the delimination, priority areas, etc. These have to be considered at planning and construction of ability- and priority areas for wind power plants. Some countries have positive/negative criteria or guidelines produced. Depending on the height of the wind power plants they are spatial significant. Regional planning procedure is needed when wind power plans have a specific height (depending on the county, Northrine-Westfalia = 100 m). Environmental Impact Assessment is needed in some cases. Often positive plans are produced. It is often possible to specify exceptions from exclusion areas for example for little single wind power plants. Immission control procedures are possible.

PV: It is to differentiate between big open space solar panel parks and solar panels on roofs of buildings. PV on roofs and buildings are not relevant for spatial planning. But the country development plan describe objectives, targets, principles of open space PV park developments. Solar panel parks can have a regionally significant impact. Impact of solar parks is in general the land consumption and the change of landscape but these are less spatial significant in comparison to wind power. Objective of the planning should be the securing of ability- and priority areas for PV. It is possible to pin the planning priority of PV in settlement areas. It is to avoid: using competiveness, uncontrolled development activities, negative environment impacts.

Biomass: Determination of objectives and principles. For spatial planning is the question of regionally significance important. This has to be proofed in single cases (e.g. size, number, spatial context, land use changes). It is possible to use spatial planning for the determination of ability- and priority areas. In a positive plan it is also possible to describe potentials for spatial significant facilities including areas for cultivation of biomass. Also the determination of areas with potentials for the use of waste biomass could be sensible (e.g. bio municipal waste, manure, green waste). For sensible areas (e.g. nature, flood safety) a negative planning is possible. Informal planning through energy- and climate protection concepts can be helpful. 

3. Regional level
Wind: Regional plan is for the concretisation of the requirements of the county development plan. The regional plan can also be used for the localisation of ability- and priority areas for wind power. The regional planner has abroad discretionary power for the site designation. In Germany for example it is forbidden to produce a single negative planning which prohibits wind power use in general.  Wind parks located close to wetlands has its risks because of birds and bats.

PV: It is to differentiate between open space big solar panel parks and solar panels on roofs of buildings. Solar panel parks can have a regionally significant impact. The regional plan concretises the requirements of the country development plan. Favoured areas for solar panel parks should be brownfields or other abandoned sites. It is possible to make positive plans to foster the use of PV. But this is often problematic because of forest areas, flood protection areas etc. The regional planer has the possibility to underline a positive development by consideration of favour or exemption criteria.

Biomass: Regional plan is for the concretisation of the requirements of the county development plan. It is possible to use regional planning for the determination of ability- and priority areas (e.g. determination of agriculture for production of renewable resources). Requirements for the ecological agreeability of the technique are sensible.

Geothermal: The regional plan concretised the content of the country development plan. But these techniques are mostly not regionally significant. However, to foster such technology through regional planning it is possible to describe a balanced energy mix for increasing the use of renewables. Furthermore it is possible to identify/regulate a reservation- or priority area for the implementation of large scale geothermal supply. The competition between geothermal uses and other purposes of the underground are not finally solvable on the regional planning level.

CHP: please see Module 4.1.

Hydropower: Positive analysis in regional planning can be an element for the localisation of sites. Use of formal regional development plan, or use of an informal instrument like the regional development concept. 

4. Local level
Wind: For the background of noise and flicker effects it is not possible to develop wind parks in all areas of municipalities. A criterion to consider is the distance to existing and planned housing areas. For the planning process it could be sensible to have overall distance guidelines. The land development plan can be an instrument for the identification of concentration areas for wind turbines. This can be an important planning instrument to avoid conflicts with citizens in an early stadium. Furthermore municipalities can use the local binding land use plan – according to the regional plan – to foster the installation of wind turbines. But they can also by consideration of planning criteria’s use the areas for other purposes. For wind parks an Environmental Impact Assessment is needed. Installation in forest areas becomes more common for wind power plants with 200 m high. A precise choice of the site is needed then which includes a case oriented analyses of impacts (incl. infrastructure). If a wind plant is spatial significant depends on the height, the localisation and the impacts on spatial functions. 

PV: It is possible to develop a concept for the localisation of PV parks in the municipality area. The localisation can be described in the local land use plan. For the installation of an open space PV park is mostly a binding land use plan required (in Germany for example to achieve funds). It is possible to define that used PV have little reflexions or the deconstruction after use. For the installation of solar panels on roofs no planning permission process is needed. Positive planning is possible. Binding land use plans can define the use of renewable energies for new settlement developments. Also solar friendly localisation of building can be described. For PV planning in urban areas and good practice examples please see the publication “Planning for Urban Scale Photovoltaic Systems“ of the IEE project PVupscale (2008): http://www.pvupscale.org/IMG/pdf/Planning_for_urban_scale_photovoltaic_systems.pdf

Biomass: The local planning can be both for technical facilities as well as for crop areas. Technical facilities include combustion and gasification plants. A privilege for outdoor areas can be verified for such plants but specific conditions have to be fulfilled. Furthermore the deconstruction of facilities after use. In general the plants can be considered as commercial or industrial. Areas for such plants are: commercial or industrial areas, special areas, supply zones, if necessary also in village, mix or core areas, close to settlements for their supply. Immission of the plants have to be considered.     

Geothermal: The municipal level has to consider the regional development plan. The use of a land use development plan for determination of areas for deep geothermal use is only partly sensible because it is not easy to estimate the productivity of a site. If public interest are affected a binding land use plan is needed. Impacts of the deep geothermal plant have to be considered.

CHP: please see Module 4.1.

Hydropower: Planning assessment procedures can be used to describe the public needs. Small hydropower facilities in rivers can be considered in local binding land use plan.

General:
Costs from the production of electricity via fossil fuels and nuclear power are mostly not cover negative environmental effects from mining, emissions, nuclear waste disposal. Follow-up costs are higher by using such conventional energy sources in comparison to renewable energies. Furthermore actual non sustainable conventional power production facilities (e.g. coal or nuclear) getting indirect funds/subsidies by the governments. A study produced for Greenpeace Germany came to the result that the additional costs for conventional energy production are higher than the funding of renewables in Germany.

A strong renewables sector does not only reduced CO2 emissions, but it is also synonymous with sustainable economic growth, reduced energy import dependence, and an overall increase in export opportunities, regional development, high quality jobs and European industrial leadership.

The deployment of renewable energy gives a strong impulse to job creation and regional development. According to European Renewable Energy Council the generation of new jobs is closely linked to the production of renewable energies (http://www.erec.org/statistics/jobs.html). In 2005 = 230 000 employees and in 2009 = 550 000 employees.

Wind power:
According to the International Energy Agency (IEA) wind power technology continues to improve rapidly, and costs of generation from land-based wind installations continue to fall. Wind power is now being deployed in countries with good resources without any dedicated financial incentives (see: http://www.iea.org/publications/freepublications/publication/name,43771,en.html).
Onshore wind power is in regions with suitable wind conditions competitive to conventional energy sources. For example in the USA a new wind park will be installed by 2015 with 1050 MW (660 000 households) despite the actual exploitation of shell gas there.


Photovoltaic (PV):

In general the costs for PV have decreased in the last years rapidly. According to the EPIA factsheet: The value chain includes research and development, production and installation of the PV. Regardless of where they are manufactured, more than 25% of the value of PV modules installed in Europe is created in Europe. The number reaches 36% when considering exports. Around 58% of the value of the PV supply chain in the EU market is created in Europe. The EU value rises to 64% when considering exports to non-EU markets. In Europe 2012 the number of full time employment (FTE) reaches around 265,000 direct jobs.  Furthermore the user/owner of the PV can – depending on the national market/funding situation – earn money. See EPIA factsheet: http://www.epia.org/index.php?eID=tx_nawsecuredl&u=0&file=/uploads/tx_epiafactsheets/Fact_Sheet_on_the_PV_Value_Chain.pdf&t=1387277294&hash=f36545a0bca75a6d0824572258b7a9e6822d435a

Biogas plants:

The use of bio materials for producing energy (power and heat) could strengthen the local economy when local products are in use as fuels. 
- purchasing costs or opportunity costs for land which is needed for the biogas plant and slurry storage;
- model of the biogas plant;
- size and dimensioning of the biogas unit
- amount and prices of material
- labor input and wages
- the degree of participation of the future biogas user and his opportunity costs for labor.

CHP: Four parameters affect the economic viability of a cogeneration system: technology costs, energy prices, operating regime and policy measures. Where there is a more or less constant demand for heat and a demand for electricity CHPs can be considered as an option. Through efficient use of fuel, for instance using CHP, countries would need fewer resources to satisfy the energy needs of its population, reducing dependence on importing fuel from abroad, or increasing opportunities to export indigenous fuels. This, in turn, can improve a country’s balance of payments. (Delta Energy and Environment, 2009).

Hydropower:
- Average investment costs for large hydropower plants with storage typically range from as low as USD 1 050/kW to as high as USD 7 650/kW while the range for small hydropower projects is between USD 1300/kW and USD 8000/kW. Adding additional capacity at existing hydropower schemes or existing dams that don’t have a hydropower plant can be significantly cheaper, and can cost as little as USD 500/kW.

- Annual operations and maintenance costs (O&M) are often quoted as a percentage of the investment cost per kW. Typical values range from 1.% to 4.%. Large hydropower projects will typically average around 2.% to 2.5.%. Small hydropower projects don’t have the same economies of scale and can have O&M costs of between 1.% and 6.%, or in some cases even higher.

- The cost of electricity generated by hydropower is generally low although the costs are very site-specific. The levelised cost of electricity (LCOE) for hydropower refurbishments and upgrades ranges from as low as USD 0.01/kWh for additional capacity at an existing hydropower project to around USD 0.05/kWh for a more expensive upgrade project assuming a 10 % cost of capital. The LCOE for large hydropower projects typically ranges from USD 0.02 to USD 0.19/kWh assuming a 10.% cost of capital, making the best hydropower power projects the most cost competitive generating option available today. The LCOE range for small hydropower projects for a number of real world projects in developing countries evaluated by IRENA was between USD 0.02 and USD0.10/kWh, making small hydro a very cost competitive option to supply electricity to the grid, or to supply off-grid rural electrification schemes. Very small hydropower projects can have higher costs than this and can have an LCOE of USD 0.27/kWh or more for pico-hydro systems.

- Significant hydropower potential remains unexploited. The technical potential is some 4.8 times greater than today’s electricity generation. The total worldwide technical potential for hydropower is estimated at 15 955 TWh/year.

- Hydropower, when associated with storage in reservoirs, contributes to the stability of the electrical system by providing flexibility and grid services. Hydropower can help with grid stability, as spinning turbines can be ramped up more rapidly than any other generation source. Additionally, with large reservoirs, hydropower can store energy over weeks, months, seasons or even years. Hydropower can therefore provide the full range of ancillary services required for the high penetration of variable renewable energy sources, such as wind and solar.
Source IRENA - please see: http://www.irena.org/DocumentDownloads/Publications/RE_Technologies_Cost_Analysis-HYDROPOWER.pdf

Concentrated Solar Power (CSP):

Please see a study to macro-economic issues here: http://www.estelasolar.eu/fileadmin/ESTELAdocs/documents/Publications/Macroeconomic_Impact_2011.pdf

Geothermal:
- field costs, including surface exploration, drilling, field development and reservoir management. This is also higly dependent on the field specifics (resource temperature and pressure, reservoir depth and permeability, etc.).
- plant costs, including machinery, equipment, design, engineering and civil works.

Description of the most innovative aspects involved

The production of renewable electricity is a necessary technique for the transformation of our energy systems. Most innovative are:

  • safe, clean (PV is quiet to operate)
  • minimal CO2 emissions
  • decentralised production facilities
  • possible regional adding value
  • highly reliable
  • require virtually no maintenance
  • operate cost-effectively in remote areas and for many residential and commercial applications
  • flexible and can be expanded at any time to meet your electrical needs
  • give increased autonomy – independence

Wind power:

  • Power to gas is seen as a future source for the production of gas which is useable for many purposes.

CHP:

  • offers energy savings of 15 - 40% when compared to the separate production and supply of electricity and heat from conventional power stations.

Biogas plant:

  • Keeping manure and waste in a confined area and processing them in the digester reduces the amount of pollutants in the immediate environment and increases sanitation;
  • The sludge remaining after digestion is a good fertilizer, increasing land productivity (and farm incomes).
  • The release of methane is avoided thus contributing to climate mitigation.
  • Biogas can contribute to replace fossil fuels, thus reducing the emission of GHGs and other harmful emissions;
  • By tapping biogas in a biogas plant and using it as a source of energy, harmful effects of methane on the biosphere are reduced;
  • Industrial estates can, by processing their waste in a biogas plant, fulfill legal obligations of waste disposal while at the same time, generate energy for production processes, lighting or heating;
  • Municipalities can use biogas technology to solve problems in public waste disposal and waste water treatment (GTZ, 1999);
  • It’s a natural waste treatment process;
  • Requires less land then anaerobic composting;
  • Reduces disposed waste volume and weight to be landfilled;
  • It generates high quality renewable fuel proven to be useful in a number of end-use applications
  • It significantly reduces GHG emissions
  • It maximizes recycling benefits
  • Considering the whole life-cycle, it is more cost-effective then other waste treatment options (IEA Bioenergy, Task 37, 2005).

Geothermal:

  • Geothermal energy is already being used in a large number of thermal and electric power plants
  • Clean, renewable, constant and available worldwide
Innovations and social aspects

Wind power:

In terms of other ecological effects related to the installation, the turbines have a relatively small environmental footprint and are often constructed on agricultural or brownfield sites, which limit their impact on local habitats or ecosystems. Although wind energy has a net positive impact on climate change mitigation local environmental impacts must also be considered. The most well publicised potential issue is the impact that wind turbines can have on bird and bat populations due to collisions. It can generally be said that the level of acceptance of wind parks onshore is high if appropriate measures are taken to ensure the limited noise and shadow effects do not affect local communities. Only through consultation and meetings with stakeholders can the awareness of local communities be improved and potential local benefits made clear.

Geothermal facilities:

It could contribute to a better income distribution towards local municipalities as the operation and management of geothermal facilities bring employment and increased economic activity in the regions where they are located. The employment will involve skilled, specialised jobs, which may not yet be available in these regions. This would require training of local people and/or hiring experts from other places.

Related good Practice Examples:

Citizens Solar Power Plants in Vienna - Solar Energy for Everyone!

Links, literature to wind power

(also available in German, Italian, Hungarian, Swedish)

 

(also available in German, Italian, Hungarian, Swedish)

 

http://www.ewea.org/wind-energy-basics/

http://www.thewindpower.net/windfarms_europe_en.php

http://ec.europa.eu/energy/renewables/studies/wind_energy_en.htm

http://www.windplatform.eu/fileadmin/ewetp_docs/Structure/061003Vision_final.pdf

http://www.iea.org/media/freepublications/technologyroadmaps/foldout/WIND_Foldout.pdf

Impuls - Praxisleitfaden Bürgerbeteiligung (German)

Links, literature to CHP

EEA, 2012, European Environmental Agency, Combined heat and power (CHP) (ENER 020) - Assessment published April 2012. See: http://www.eea.europa.eu/data-and-maps/indicators/combined-heat-and-power-chp-1/combined-heat-and-power-chp-2

A.C. Oliveira, et al.: A combined heat and power system for buildings driven by solar energy and gas, 2002. See: http://www.sciencedirect.com/science/article/pii/S1359431101001107

Links, literature to Power to Gas

http://energytransition.de/2013/06/power-to-gas-competitiveness/

http://www.gtai.de/GTAI/Navigation/EN/Invest/Industries/Smarter-business/Smart-energy/power-to-gas.html

http://www.powertogas.info/

http://www.hydrogenics.com/products-solutions/energy-storage-fueling-solutions/power-to-gas

Further documents, presentations

Specht, Power-to-Gas (P2G®): Technology and System Operation Results

RWE, ADELE – ADIABATIC COMPRESSED-AIR ENERGY STORAGE FOR ELECTRICITY SUPPLY

M. Bonte, et. al., Underground Thermal Energy Storage: Environmental Risks and Policy Developments in the Netherlands and European Union.