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Tag Archives: geothermal

Green energy for Africa

By Dave Elliott

The International Renewable Energy Agency says that Africa has the potential and the ability to utilise its renewable resources to fuel the majority of its future growth with renewable energy. It adds ‘doing so would be economically competitive with other solutions, would unlock economies of scale, and would offer substantial benefits in terms of equitable development, local value creation, energy security, and environmental sustainability’.

That seems a bold claim both technologically and economically, and also politically. But the renewable resource is very large (for solar especially) and the technologies are getting cheaper fast. However, with 54 very unevenly developed countries on the huge continent, whether the political and institutional cohesion is there for a co-ordinate push is  less certain. (more…)

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Energy in the USA

By Dave Elliott

The boom in shale gas extraction may dominate the news headlines, but renewable energy is also moving head rapidly in the USA. It currently supplies about 15% of US electricity, if off-grid use is included, and the potential for expansion is very large. A new report from the US National Renewable Energy Laboratory (NREL), ‘The Renewable Electricity Futures Study’ (RE Futures), found that the US renewable resource base was sufficient to support 80% renewable electricity generation by 2050, even in a higher demand growth scenario. It also looks at a 90% option, with 700GW of wind and solar PV.

To accommodate this large variable supply input, there would have to be major upgrades to the grid and up to 100GW of balancing back up/ load shifting/storage. But NREL’s hourly modeling found that, with this backup in place, demand could always be met, even at peak times, although 8-10% of wind, solar, and hydro generation would need to be curtailed e.g. at times of low demand, under an 80%-by-2050 RE scenario, and more storage would be needed in the 90% scenario.


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Japan’s Energy Plan

By Dave Elliott

In the aftermath of the Fukushima nuclear disaster in March last year, Japan has been trying to develop an alternative approach to energy supply and use, based on energy efficiency and a major commitment to renewables, including a new quite generous Feed-In Tariff for PV solar, a 1GW off shore wind programme and more support for other marine renewables- offshore projects obviously make sense in a country where land is at a premium. I outlined some of the offshore wind projects in an earlier Blog- they included floating wind turbines off the coast from Fukushima:

In addition the government has decided to allow geothermal energy projects in newly opened areas of national parks. It is claimed that this could result in the development of up to 2 GW of capacity by the 2020s. As a very symbolic start, a 500 kilowatt geothermal plant is to be installed at the Tsuchiyu Onsen hot spring in Fukushima City. Some new biomass projects have also been started, including algae production for biofuels.


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EGU 2012: going green on (and under) the ground

By Liz Kalaugher

The thousands of delegates congregating in Vienna this year will find the EGU making further efforts to “green” the meeting – badge lanyards are made from bamboo fibre rather than PET and the conference schedule is smaller to save paper. It seems only appropriate, since many of the sessions at the conference will focus on the cryosphere (shrinking), climate (warming), natural resources (under pressure) and energy. But are such measures just a drop in the ocean, especially as environmental issues appear to have fallen down the priority list for many governments?

Indeed, governments received a call for action within the first half hour of the conference opening, with Millie Basava-Reddi of the International Energy Agency Greenhouse Gas R&D programme (IEAGHG) stressing the need for investment in carbon storage, in her talk presented by session chair Michael Kühn due to a delayed flight.

While the G8 nations would like to see 20 carbon capture and storage projects up and running by 2020, the IEA target is 100 by 2020 and 3,400 by 2050. The agency’s latest assessment, however, indicates that while 20 projects are feasible for 2020 its own roadmap isn’t, with just 50 projects likely by 2025. Worldwide there are currently 14 large-scale integrated projects in operation or execution; 2011 saw 74 large-scale projects in at least the planning stage. Basava-Reddi called on governments to allow for long project lead times – up to fifteen years – and to help to provide up-front investment.

The challenges for carbon capture and storage in many cases mirror those for other subsurface technologies such as geothermal energy. Indeed Kühn’s group at the Helmholtz Centre Potsdam, Germany, is researching how brine extraction from saline aquifers could help reduce the pressure rise induced by the addition of carbon dioxide, whilst at the same time providing geothermal heat.

There are a large number of issues in geothermal energy that need substantial research efforts, explained Adele Manzella of CNR Institute for Geosciences and Earth Resources, Italy. The upper 3 km of the Earth’s crust could provide 60,000 times our current power consumption; the only snag is where and how to access that power. The up-front costs are high and it’s hard to forecast production, especially since there is a lack of data on geothermal potential. But once systems are set up the energy produced is cheap compared with other types of renewable energy, since power is provided 24 hours a day.

The European Energy Research Alliance has set up a Joint Programme on Geothermal Energy, said Manzella. Areas under study include assessing Europe’s resources for geothermal power, how to mitigate induced seismicity in reservoirs, and high-performance drilling.

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EGU 2011: CCS and geothermal – the best of both worlds?

By Liz Kalaugher, EGU General Assembly in Vienna

Although they have a common goal – lowering the carbon footprint of energy systems – carbon capture and sequestration (CCS) and geothermal energy could one day end up in competition for both suitable geological sites and funding. Frank Schilling of the Karlsruhe Institute of Technology, Germany believes there’s a solution; he reckons that the two technologies could be combined to the benefit of both.

“Our storage capacity is limited so we must use the resource wisely,” he told the press at the EGU Assembly in Vienna.

Not only could the two technologies share expertise in drilling technology and reservoir management, he believes, but geothermal could enhance the storage potential of CCS. A typical geothermal energy system removes hot water (around 40 degrees C or higher) from thermal aquifers around 1000 m below the ground, extracts the heat and returns cold water to the depths.

Since this cold water is denser than the hot water it’s replacing, it potentially provides more pore space for storing carbon dioxide. In turn the addition of carbon dioxide could prevent any problems for the sub-surface caused by the introduction of negative pressure.

For geological formations where there are multiple barriers at different depths, an alternative combined system could see hot water removed from the thermal aquifer and carbon dioxide pumped in. Following heat extraction, the cold water could be returned to a higher level – the resulting negative pressure gradient would make leakage of carbon dioxide from below less likely. According to Schilling, halving the effective pressure on the caprock doubles the security of the system or doubles the storage space.


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Underground energy

Geothermal energy is coming
back in favour in the UK as an energy option, after some years in the
wilderness. A major geothermal “hot dry rock” test project in Cornwall was
abandoned in the 1980s after it was assessed as not being likely to produce
sufficient energy for electricity production, and although Southampton
persevered with a more conventional aquifer heat-based system, geothermal was
basically left to other countries.

There is now over 11 GW of
installed geothermal aquifer electricity generation capacity around the world
and even more heat supplying capacity, but deep “hot rock” geothermal
technology has recently had a renaissance, in part due to the availability of
improved drilling techniques developed in the oil industry.

Enhanced geothermal systems
(EGS) as they are now called, are beginning to move towards commercialization.
A 2.9 MWe plant is operating commercially in Landau, western Germany, while
projects are now being developed in Australia, the US and Japan, and plans are
taking shape for a 3 MWe plant in Cornwall, at the Eden Project.

In its recent Renewable
Energy Strategy, the UK government said that it would “commit up to £6 m to
explore the potential for deep geothermal power in the UK helping companies carry out exploratory work needed to
identify viable sites”.

Depths of 3,000 to 10,000
metres can now be reached, with water pumped down to be heated by the hot rocks to around 200 degrees
centigrade. Feeding back to the surface, this water can then be used to drive
turbines to generate electricity.

Martin Culshaw of the
Geological Society’s engineering group, said: “Cooling one cubic kilometre
of rock by one degree provides the equivalent energy of 70,000 tonnes of coal.
This has the potential of equalling the nuclear industry in providing 10–20% of
Europe’s energy.” Geothermal systems have the
big advantage over many other renewables of supplying “firm” continuous power,
although they aren’t strictly 100% renewable, in that heat wells exhaust the
local heat resource over time. But it’s topped up eventually by the heat from
deeper inside the earth- derived from nuclear isotope decay. That makes it one
form of nuclear power that seems benign.

However there can still be
problems. Iceland has been developing geothermal electricity production on a
large scale, but as Lowana Veal has reported in IPS News,
there have been concerns about emissions of hydrogen sulphide gas. Moss in the
area was being effected. Levels were well below what was thought have any
health risks for humans, but it is being monitored. H2S can be filtered out of
the steam and water vapour that is emitted by geothermal plants, or it can be
reinjected back into the well in a closed loop binary system. But that all adds
to the cost.

Perhaps more importantly,
carbon dioxide gas is also present. To deal with this a “Carb Fix” programme is being
developed.  The idea is to dissolve
the CO2 in water under high pressures and then pump the solution into layers of
basalt about 400–700 m underground, in the expectation that the dissolved CO2
will react with calcium in the basalt to form solid calcium carbonate. The
project is a form of carbon capture and storage (CCS). But rather than filling
empty oil or gas wells with CO2 gas under pressure, mineral storage offers a
safer bet, since there is less chance of leakage.

There may also be a
potential problem with earthquake risks from deep drilling in some locations.
Drilling kilometres down and then pressurising the system can lead to release
of geological stresses, lubrication of fissures and small earth tremors. There
were some recorded for example with a geothermal project in Switzerland in
2006, when water was injected at high pressure into to 5 km deep borehole. A
shock measuring 3.4 on the Richter scale was detected, which caused local
alarm, but evidently no injuries or serious damage, although further work was
halted. There was a 3.1 scale tremor subsequently. This issue has recently led to concerns about some of the
new German projects.

Problems like this apart,
the prospects for geothermal seem good. The USA is in the lead in terms of geothermal electricity production,
and has around 4,000 MW of new capacity under development. recently
put £5.4 m into enhanced “hot rock” geothermal systems , supporting three new
projects in the USA, and Obama allocated $350 m to geothermal work under the new economic stimulus funding.

The resource potential is
very large. The US Department of
Energy has suggested that in theory the US could ultimately have at least
260,000 MW of geothermal capacity. Large resources also exist elsewhere in the
world and there are many projects in operation or being developed. As already
mentioned, Iceland is a leading user, but the Philippines, which generates 23%
of its electricity from geothermal energy, is the world’s second biggest
producer after the US the United States. It aims to increase its installed
geothermal capacity by 2013 by more than 60%, to 3,130 MW. Indonesia,
the world’s third largest producer, plans to have 6,870 MW of new geothermal
capacity over the next 10 years – equal to nearly 30% of its current electricity
generating capacity from all sources. Kenya has announced a plan to install
1,700 MW of new geothermal capacity within 10 years – 13 times greater than the
current capacity and one-and-a-half times greater than the country’s total
electricity generating capacity from all sources.

Finally, the use of ground-source heat-pump technology is also expanding rapidly, with perhaps 200,000 units having been installed in domestic and commercial buildings around the
world. This is also sometimes
labelled as “geothermal”, not really completely correctly, since at least for
surface based heat pipe extraction, the heat is mostly ambient heat ultimately
derived from the sun, not from deep in the earth. But some heat pumps do use
deeper pipes and they can also be used to upgrade the value of geothermal heat.
In addition, heat can be stored in the earth via underground piping, creating
local underground heat stores.

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