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Regulation over short period can be done with:

- hydropower. By increasing the generating capacity it is estimated

that the necessary complement for 5
With the existing water power 3
(72).

fuel cells

·

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7 GW windpower is achieved.

5 GW of windpower can be combined

combined generation of power and electricity. Through heat storage variations in electricity demand over 24 hours can be partially balanced.

- regulation of demand for electricity in housing. E.g. the
ancillary energy need for space heating can be met during times
of low load or when the production of electricity exceeds demand.
Regulation (switching on and of) can be made by signals of radio
3
frequency sent over the electricity grid. A water tank of 8 m
can store approximately 300 KWh in the temperature interval
20 - 50°C which is equivalent to the heat need of a single home
during approximately 3 winter days.

regulation of industrial energy demand. In processes where process heat is generated with electricity the load can be influenced by the use of heat storage or by producing hydrogen through electrolysis of water, which is stored and burnt at need.

besides the above there are further measures for regulation needed. Installations where electric energy is stored over relatively short periods of time are needed. These can be pump storage (electric energy is converted to potential energy by pumping water to a lake or dam: electric energy is produced by hydro-electric generation at need). Other alternatives could be mechanical fly-wheels or

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production of hydrogen which is stored and converted to electricity in hydrogen fuel cells.

The need for seasonal storage arises primarily with solar cells (also with hydropower where however large dams already exist). As discussed in section 2.4 a maximum of 35 - 40% of the electric energy from solar cells need be stored from sunny summer months to winter months. Storage of hydrogen over longer periods seems to be relatively expensive (62). Another alternative is to supply oxygen and hydrogen from electrolyzed water to methanol production. The solar electricity would thus be connected to the energy system in the form of methanol. We utilize 20 TWh of the production of solar cells in this way. Through the existence of hydrogen storage (and oxygen storage) it would seem possible to absorb a (smaller) part of the load variations.

By having a large proportion of electricity production occur near the user and some of the evening out of the load occur at the point of utilization, the demand for high capacity electricity grids can be limited (compared to if the load variations were to be absorbed only on the production side with large installations nydropower, pump storage etc.).

The losses in the electricity system have been estimated at approximately 21 TWh, of which distribution losses are 15 TWh and losses in short time storage approximately 6 TWh. Distribution losses in 2015 are assumed to be 8 %. Today they are approximately 10 %. The lower figure is justified by shorter transfer distances. Electricity for end use is thus 148 TWh. (20 TWh from solar cells used in methanol production is not included.)

Thus there does not seem to be a scarcity of electricity in Solar Sweden. This is not because the demand has been adjust towards a small proportion of electricity but because several of the renewable production methods give electricity (hydropower, windpower, photovoltaic cells). It is also because part of the heat need, primarily

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district heating in the larger cities and part of the need for process heat, cannot be supplied by direct solar heating for various reasons. This causes heat to be available for production of power from counter-pressure generation, which further increases the availability of electricity.

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We have chosen to introduce only one new energy carrier in Solar Sweden. We have chosen methanol rather than the frequently discussed hydrogen. The reason is primarily a wish to avoid building a large scale network for distribution of gas in the country, since this is both expensive and strongly determines options for locating industries and other activities. Hydrogen can however be available locally in large quantities.

Methanol, CH2OH, is a liquid. One can consider it as two molecules of hydrogen with a molecule of carbon monoxide added to make it liquid. The energy density of methanol is approximately half that of petrol. Methanol is colourless, water soluble and odourless. It freezes at - 98°C and boils at 65°C and has a density of 0.8g/cm3. In the US approximately 4 million tons of methanol were produced in 1972. It was sold at a price of approximately 0.25 Sw. Crs per litre (74, 75, 76).

A new energy carrier must be introduced in Solar Sweden, primarily to replace petrol in the transport sector. Several factors point to methanol. It is possible to store, it is liquid and can be gradually introduced into the existing transport system. Hydrogen would demand an entirely new technology without the same possibilitiy for gradual change. Gas has the same limitations.

Methanol can be produced from biomass, peat, natural gas or coal.
It can also be imported e.g. through contracts with some country

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with large resources of natural gas, where gas is not today used but burnt at the well-head due to lack of alternatives.

Methanol can be used in many ways. It burns with a clean blue flame. It can be used in combustion engines of today ́s type. Utilization in fuel cells is also a possibility, which we have assumed in the future transport sector.

An important advantage is that methanol can be mixed with petrol.
The amount can be 15 - 20 % and be used in present car engines
with very limited changes. In this way a production of methanol
can be built up. If the alternative of mixing petrol and methanol
in the pumps at petrol stations is chosen (in a similar manner to
mixing with oil for two-stroke engines) a distribution network
is also created. Use of methanol in petrol means that the lead
additive is not necessary and other emissions can be reduced.
This is of great importance and can be relatively quickly carried
out. With somewhat larger changes Ottocycle engines can be fueled
by pure methanol.

Methanol has been shown to be a useful fuel in fuel cells. A
fuel cell has been developed which has run continuously for more
than 30,000 hours on methanol and air (74). The fuel cell utilizes
tungsten carbide and coal as electrodes and sulphuric acid as
electrolyte.

Conversion of natural gas, coal or biomass to methanol entails loss of part of the energy content. So far methanol has been produced primarily from natural gas and coal. The energy conversion efficiency is today 55% at production from natural gas and 45% from coal. By more efficient reclamation of heat 75% can theoretically be reached. 65 68% is deemed a realistic level (76). Methanol has not previously been produced from wood or waste, but this ought not to be problematic

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since they can be gasified (77). The sulphur content in these fuels is lower than 0.1 %, whereas coal has 2 % or more. Since the catalysts used in methanol production are particularly sensitive to sulphur, the low sulphur content of wood and solid waste is an advantage. The conversion efficiency is 35% from wood and waste, but it can be considerably higher or lower depending on the size of the plant and the heat reclamation (77).

Surplus electricity from solar cells (during summer months) is assumed to be added to the methanol production in the form of nydrogen and oxygen (electrolysis of water)! Since hydrogen is a high quality fuel this gives a higher efficiency. We have in our calculations used an average efficiency of 55 %.' 2) Part of the

waste heat has also been utilized.

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In fuel cells the chemical energy of the fuel (rich in hydrogen) is converted directly to electricity (direct current) without an intervening combustion or heat cycle. No cooling water is needed. A single cell produces a voltage of 0.5 1 V with a current proportional to the area of the cell. The cells are connected in series. In this way they are combined to modules.

1)

Electrolysis of water to hydrogen and oxygen has today in commercially available plants an efficiency of 60 - 70 %. The interest in developing efficient methods of electrolysis has previously been weak since hydrogen for industrial use has been obtained cheaper and more simply from oils or methane (73). The theoretical efficiency is 120 % because the cells take heat from the surrounding environment (8). We assume here that it is possible to develop the processes and to use waste heat from methanol production to an efficiency of 100% in converting electricity to hydrogen and oxygen.

2) In accordance with what is shown in EFA 2000 (11) page 97,for conversion of biomass to methanol at the level of technological development expected for 1990.

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