The Germans and "some" French have been looking at how a largely renewable
energy system may operate in the future.
The University of Kassel (Fraunhofer-Institute IWES for Wind and Energy
Systems Technology) has also looked at a renewable energy based smart grid
with there modeling of a virtual renewable power plant using wind and solar
photovoltaic as the base load and bio-methane and hydro as make up and
peak load.
http://www.kombikraftwerk.de/index.php?id=27http://www.youtube.com/watch?v=tR8gEMpzos4+++++++++++
Gregor Czisch whilst at Kassel doing his PhD has also modelled a renewable
energy network based on a HVDC super grid for Europe. This modelled a
number of diffrent scenarios based on todays technologies to arrive
at an economic cost via mathematical optimization. A CO2 neutral system
based on renewables was found to be the lowest cost option for Europe.
http://kobra.bibliothek.uni-kassel.de/handle/urn:nbn:de:hebis:34-200604119596http://nbn-resolving.de/urn:nbn:de:hebis:34-200604119596and english translation may be purchased at the IET Institute for
Energy Technology
http://www.theiet.org/resources/books/renewable/scenarios.cfm+++++++++++++++++
Now the Fraunhoffer Institute-IWES (Dr. Michael Sterner) and ZSW -
(Centre for Solar Energy and Hydrogen Research- Baden-Württemberg
(Dr. Michael Specht) , et al have been ooking at the integration of all of
the different renewable options and in particular using SNG Synthetic
Natural Gas as an energy storage vector of excess renewable energy.
This analysis has also looked at the systems efficiency from an exergy
basis (2nd law of thermodynamics).
Fraunhofer Institute + summary of proposal
http://www.brighthub.com/environment/renewable-energy/articles/78303.aspxSpecht renewable power energy methane
http://www.solar-fuel.net/fileadmin/user_upload/Publikationen/Wind2SNG_ZSW_IWES_SolarFuel_FVEE.pdfSterneer thesis : "Bioenergy and renewable power methane in integrated
100% renewable energy systems" that modeled the German energy sector
http://www.uni-kassel.de/upress/online/frei/978-3-89958-798-2.volltext.frei.pdfIt is largely a renewable energy system based on energy efficiency
(smart grid, device and building efficiency,...),
renewable energy (wind, hydro, tidal, ocean river current, solar
photovoltaic or thermal, geothermal natural or deep rock, ...)
and low carbon biomass energy (timber, SRC, gasification, bio-gas ...)
systems.
The WBGU German Advisory Council on Global Change has been particularly
looking at the implications for low carbon biomass cycles how much to use
without disturbing food production or soil fertility, etc. were
fed into the above studies.
Future Bioenergy and Sustainable Land Use, WBGU German Advisory Council
on Global Change
http://www.wbgu.de/fileadmin/templates/dateien/veroeffentlichungen/hauptgutachten/jg2008/wbgu_jg2008_en.pdfThe hydrogen would be produced via electrolysis, or membrane separation of
water (or whatever more energy efficient process that is developed) from surplus
renewable electrical energy that cannot be used instantly used by
the electric grid. CO2 would be separated from carbon based fuel wastes
and instead of just injecting CO2 into underground reservoirs, it would be used
to create methane (SNG Synthetic Natural Gas) via the Sabatier reaction.
CO2 + 4 H2 > CH4 + 2 H2O
http://en.wikipedia.org/wiki/Sabatier_reactionWhen the methane is used in CCGT for peak or make up electrical energy the
CO2 would be extracted to make more methane.
The German gas network for example has about 2 months of energy storage
capacity. This is more than enough stockage
to overcome shortfalls when the sun or wind is not available.
Importantly the CO2 is given an economic value as a corposant of a fuel
rather than a cost as in
CCS Carbon Capture and Storage.
It is only about 50% efficient but it would be one of the last ports of
call after other more efficient renewable energy storage devices such as
pumped hydroelectric storage (~70% efficient), compressed air storage,
etc. are used.
Hydrogen is an ideal cycle but faces problems of economic cost, longevity
of fuel stacks, scalability, etc.
For example transport of hydrogen by pipeline would require stainless
steel or perhaps composite fibre network
that would need to be constructed. Hydrogen though could be used directly
in small scale local cogeneration fuel cells perhaps topped up with local
hydrogen fom local digesters making bio-methane from the separately
collected fermentable proportion of town waste.
The renewable energy scenarios have been modelled on a n hour by hour
basis up untill 2050 when in both countries nuclear energy would be
phased out.
The thesis "Bioenergy and renewable power methane in integrated 100%
renewable energy systems" modelled the German energy system in 2050 :
http://www.uni-kassel.de/upress/online/frei/978-3-89958-798-2.volltext.frei.pdfFig 6.2.1 page 174/230 for the year 2050 you will see that 5GW of
renewable power methane (RPM) (the yellow hatched area below the 0GW line)
using the surplus electrical renewable energy.
In France the Negawatt Institute "Scénario négaWatt 2011" modelled the
French energy system in 2050 :
http://www.negawatt.org/telechargement/SnW11//negaWatt_scenario_2011-Partie2.pdfthe sankey diagram page 32/41 indicates 33TWh total of methane
(Méthanation) : 13TWh for heat via the gas grid
and 20TWh as a carburant for transport.
The whole system is based on energy efficiency, renewables and low carbon
biomass cycles. The methanation cycle
is just a part of the whole system but helps solve the problem of
occasional intermittancy.
It is also a pragmatic and cost effective use of existing infrastructure
and resources in order to develop a renewable energy system in probably
a very economically constrained future world.
Solar Fuel GmbH a company set up by Fraunhofer et al to develop and
commercialise the technology
http://www.solar-fuel.net/en/the-challengeThe Negawatt Institute (France) has modelled in detail the French energy
system based on using efficiency and renewable energy with some
SNG conversion. This would allow the nuclear industry would be phased out
by 2050.
http://www.negawatt.org%2Fscenario-negawatt-2011-p46.html++++++
The SRU The German Advisory Council on the Environment (SRU) have also looked at linking Germany's energy system wih the Scandanavian system and in particular the Norwegian pumped hydro electric storage.
sru report Pathways towards a 100 % renewable electricity system
http://www.umweltrat.de/SharedDocs/Downloads/EN/02_Special_Reports/2011_10_Special_Report_Pathways_renewables.html
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