11.08.2015   BIOFUELS

Use of Renewable Energy

Although it is clear that energy generation from renewable resources will have to be incorporated into the overall consumption of energy, it has been slow to be adopted.

This has been in part due to the higher cost of renewable energy, reliance on the discov­ery of new fossil fuel sources rather than concentration on renewables, and the need for legislation to encourage these energy sources. In Chapter 1 the world’s current use of energy is given, where renewables contribute almost 12.7% of the total and nuclear 6.3% (Fig. 1.4). The use of hydroelectric, biomass and other renewables is expected to rise from 1.04 Gtoe in 2002 to 1.55 Gtoe in 2030 (Table 1.2) which is actually a slight drop on a percentage basis. A more detailed breakdown of the renewables contribution is given in Table 3.11. In 2005 the world’s total energy use was 11,434 Mtoe, where renewables, excluding nuclear power, contributed 3379 Mtoe.

Most of the renewable sources of energy are used to produce electricity and their contribution to world, EU (25) and UK electricity generation is given in Table 3.11. A modern power station, Didcot (in the UK), will have a peak output of 2000 MW and for nuclear station it is around 1320 MW. The peak electrical demand for England and Wales is 50,000 MW (50 GW). The potential contribution that the non-carbon-based renewable electricity generation could produce in the world is given in Table 3.12.

Table 3.11. Renewable fuels contribution to the global, EU (27) and UK electricity generation, excluding nuclear power. (From Dti, 2006a; BERR, 2007; IEA, 2007.)

Fuel

World

%

EU (25)

%

UK

%

Biomass

161

4.8

57

11.4

8.1

34.2

Waste

64

1.9

27

5.3

4.81

20.3

Hydro

2993

88.6

340

67.7

7.89

33.3

Geothermal

57

1.7

5.4

1.0

0

0

Solar PV

1.6

0.0005

1.5

0.003

0

0

Solar heat

1.1

0.0003

0

0

0

0

Wind

1 01

2.9

70.5

14.0

2.91

1 2.3

Tide

0.56

0.00017

0.53

0.001

0

0

Other sourcesa

8.8

0.003

7.0

1.4

0

0

Total

3379

502

23.7

(290 Mtoe)

(43.1 Mtoe)

(2.03 Mtoe)

aIncludes imports.

Table 3.12. Potential contribution of conventional non-carbon energy systems to electricity generation. (From Green et al, 2007.)

Source

Generation (EJ/year)

World electricity generation for the year 2100 (EJ/year)a

1 46

Contribution by nuclearb

38

Contribution of hydroelectric

32

Contribution of solar and windc

15

Electricity generation in 2100 (%)

58%

aIf growth is 1% per year, 146 EJ/year would be required.

bBased on 1500, 1000 MW plants operating at 80% capacity, consuming 306,000 tonnes of uranium per year.

cThe contribution at 50% wind and 50% solar would require 160,00 km2 at 2116 km2 per EJ/year (1 km2 = 10 ha).

The possible electricity that will be required in 2100 has been included in the table to indicate the possible target. However, increased legislation and the Kyoto Protocol should encourage increases in renewable energy.

In the UK, the pattern has been much the same as the world’s with nuclear and renewables producing 22.5 Mtoe in 2006 (BERR, 2007). Much of this contribution was in electricity generation. In 2005, renewable electricity generation was 4.4% (Cockroft and Kelly, 2006) not including hydroelectricity, and Table 1.4 gives the renewable energy source in terms of 1000 tonnes of oil equivalent. The major proportion comes from landfill gas and biofuels. Table 3.13 gives the peak electrical power output from some of the renewable energy systems installed in the UK at present (Dti, 2006b) and indicates some of the potentials of these systems. Small power generation systems are often connected to the distribution network rather than the main grid (400,000 volts).