Example of a sustainable energy system

A number of studies have shown that, at least technically, it may be feasible to reduce the CO2 emissions of industrialised countries by more than 80 percent within the next fifty years. A short summary of one such study for the European Union (current 15 countries) energy system is given in Figures 5.5 and 5.6.

Figure 5.5: Proposed energy system for the European Union (current 15 countries) in 2050 based mainly on renewable primary sources of energy and use of advanced efficiency end-use technologies

Source: [Nielsen and Sørensen 1998].

Figure 5.5 illustrates the composition of a proposed future energy system for the fifteen European Union countries that has been proposed by Nielsen and Sørensen [1998].

The future energy system combines a number of renewable energy production technologies such as hydro dams, wind turbines, photovoltaics, solar thermal electric plants and solar thermal heat collectors with electrical heat pumps utilising the environmental heat of the surroundings and CHP stations fired mainly by residues, traditional biomass residues and biomass from large-scale energy-crop plantations and energy forests. Land based transportation is almost entirely based on electric motors, either in battery-electric vehicles or in fuel-cell electric vehicles using hydrogen stored on-board in pressurised fuel tanks or using methanol which is reformed into hydrogen on-board. However, air and ship transport still utilises conventional fossil fuels. The

Fair market scenario for the energy system of the European Union (15 members) in 2050 (TWh/y)

Primary energy Biomass conversion Storage and Energy conversion Demand/ End use

and storage cycles transmission by CHP and energy qu ality

for electricity from losses heat pumps

So lar thermal heat 387 ren ewable energy Industry

D istr ict heat pipeline Heat p umps 45 Elect ricity 384

Biogas 258 398 299 C HP using hydrogen Add low t emp 65 Fuels 924

Gasification /Bio - 418 335 Elect ricity 384

Biomass residues 384 mass to hydro gen Gas store/pipeline H ea t 209 Hydrogen/gas 814

1877 939 258 219 E lectr icity 125

Biomass from plant at ions 2117 Households

Hydrogen store/ Heat p umps Solar heat 241 Elect ricity 318

PV elect ricity 699 pipeline 90 359 Heat p umps 185 Space heat ing 485

2149 1827 Add. low- T heat 116 Water h eat ing 57

On-sho re wind elect ricity 573 Methano l p lan t Elect ricity 342 Non-elec. cooking 24

623 274 So lar heat storage

Offsho re w ind elect ricity 610 space heat

325 196

Hyd ro power elect ricity 269 Ser vice sector

So lar heat storage Elect ricity 293

Add . small hydro power el. 222 hot wat er Add low- T heat 117 Elect ricity 293

62 45 Heat p umps 129 Other u ses 247

Solar th ermal elect ricity 421 R eve rsible fuel c ells 1T Wh=1000GWh

hydrogen input Elect ric grid Transport sector

Oil f or aircraf t and ships 540 671 602 2137 2019 Elect ricity 511

H ea t 189 Biogas 180 Road 911

Non -energy uses 1013 E lectr icity 413 Met hanol 274 Rail ( electricity) 54

Aircraft fuel 493 Air 493

En vironmental heat 269 Car bat teries Sh ip fuel 87 Wat erways 87

R eve rsible fuel c ells 911 455

T otal primar y 7762 electr ic ity input Total 4275 Total 4275

1397 1254

% fossil 20% Hydrogen import 1

Electricity import 204

system also contains an advanced reversible fuel cell system delivering CHP that utilises electricity overload from intermittent renewable sources (wind turbines, photovoltaic panels, solar thermal electric plants) to produce hydrogen which is stored in underground caverns and pressurised tanks. Hydrogen is also stored in buildings, passenger cars, trucks, buses and trains. At times when the electric load is low stored hydrogen is used for CHP production. Other energy storage options in use are vehicle batteries and pumped hydro. Biomass and biogas are used as back-up fuels, and are also used to produce methanol for transportation purposes. Furthermore, the system is based on large bulks of electricity and hydrogen being exported and imported internally between the 15 countries. And Europe as a whole is dependent on some imports of electricity and hydrogen that could be produced for example in sunny Northern Africa, where vast quantities of land could be available for large-scale centralised photovoltaic installations. Finally, the system is based on using advanced efficiency end-use technologies. Examples of such technologies in use in the transport sector are carbon-fibre ultra-light and aerodynamic fuel-cell battery-electric hybrid vehicles and ultra-large low-drag lightweight flying-wing shaped airliners powered by advanced propfan engines. Furthermore, the current electric appliances, motors etc. are considered fully substituted by advanced efficiency versions, and buildings are much better insulated offering substantially better thermal efficiency. The remaining part of the existing building stock has been retrofitted with additional thermal insulation and efficient glazing while new buildings have been built with emphasis on thermal efficiency and passive solar. Also industrial processes are assumed to be more efficient using less raw materials and energy per unit produced.

The energy system described in Figures 5.5 and 5.6 seems technically feasible in a long-term perspective, because the current energy system, as well as many infrastructures and a major part of the end-use technologies will have to be replaced within the next fifty years. But the implementation of such a system will depend much on the willingness of Europe to invest in energy efficiency and renewable energy technologies. The main arguments for building up such a system would be environmental concerns over pollution and global warming and long-term resource issues, such as exhaustion of fossil reserves. The main driver for implementing such a system is anticipated by Nielsen and Sørensen [1998] to be that the price of fossil energy is taxed to a substantial degree as compared to the current situation. This

would allow the relatively expensive energy producing technologies that are based on renewable types of primary energy to be introduced into the market.

Figure 5.6 shows, from left to right, the flow of energy from primary energy supplies over conversion, storage and transmission to delivered energy and end-use conversion in the proposed energy system. In 1990 the primary energy supply was based primarily on fossil fuels, that is coal, oil and gas, and nuclear and hydro power (the latter two being primary electricity). By 2050 nuclear is assumed to have been phased out in Europe while the main part of the fossil sources have been substituted by renewable sources, that is wind power, solar thermal, solar electric, biomass, hydro and environmental heat (from electrical heat pumps).

Figure 5.6: Overview of European energy system in 1990 and comparison to a scenario for 2050

Source: [Nielsen and Sørensen 1998].

Figure 5.6 illustrates in broad terms the differences between the European energy system in 1990 and the proposed system for 2050. As can be seen from the illustration, the total amount of energy delivered to the consumers has been cut by almost 60 percent even though the end-use energy service level is 44 percent higher than today,

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because much more energy efficient end-use technologies are in use. Similarly, the amount of primary energy needed to fulfil those needs is only about 56 percent of what is needed today, mainly because half of the primary electricity produced from renewables is being transmitted directly to consumers without considerable losses. The other part of this electric production is converted into hydrogen that is being stored for later use and thereby incurring some energy losses. Furthermore, the use of renewable sources of energy has allowed for phasing out most uses of fossil fuels.

In the proposed energy system commercial civil air transport still remains one of the few users of fossil fuels, using about 12 percent of the final energy consumption in Europe and 6 percent of the primary consumption, which equals 91 percent of the total remaining fossil uses, excluding non-energy uses. Note that these figures are based on the assumption that the specific fuel intensity of the global aircraft fleet has been reduced by 50 percent as compared to today while Europeans are assumed to only travel three times as much by air as in 1990. Three times more passenger air travel in Europe in 2050 as compared to 1990 is a relatively low figure as compared to what is currently envisaged by the commercial civil air transport industry itself. The latest industry forecast suggests that global passenger air travel might triple already in 2020 as compared to 1999 [Airbus 1999]. If air traffic continues to grow at the current pace in Europe the sector might well consume at least three to five times as much jet fuel in 2050 as what is envisaged in the European scenario suggested here for 2050.

Thereby, commercial civil air transport may be using up to more than 50 percent of the total final energy use and up to around 30 percent of the total primary uses.