plant
boiler
22
Fuel boiler
Fuel 133
Heat 40
Fuel 100
Heat 40
CHP
40
18
40
45
P5
Transport (30)
Transpo (30)
33
33
Wind (75%) 39
Electric 30
Wind (50%) 19
Electricity 30
10
8
13
19
By Rasmus Lund, Ph.D., Assistant Professor, Department of Planning, Aalborg University
Heat pump
Heat pump
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25
demands will cut the total need for energy input and reduce costs for the energy systems and further improve the benefit of the sector coupling. Hence, the discussion in this article will be equal or more valid also in this situation. CHP Fuel 71 Heat 40 Transport (30) 38 15 CHP Fuel synthesis Fuel 39 27 8 11
Heat 40
In order to reach an energy system based on renewable and sustainable resources in an efficient way, we need to transform our energy systems to allow fluctuating renewables to replace fuel consumption. This can be done through a coupling of the main energy consuming sectors via supply and conversion technology that links the production from fluctuating renewables to demands across sectors to reduce the need for fuel. Here we take a look at the effect on the whole energy system as 25%, 50% and 100% renewable electricity is introduced.
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Transp (30)
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33
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Figure’s legend and explanation
Heating
Electricity
Fuel
Conversion unit
Supply / demand
The figures illustrate energy systems as primary energy input on the left side, conversion units in the middle and demands on the right side. The demands are the same in all the four figures, and the differences illustrate different ways of covering the same demands. The numbers for the “Transport” sector do not add up to 30 because these include efficiencies of different vehicle types to cover the transport demand. The difference is mainly between internal combustion engines and battery electric vehicles.
THE NEED TO TRANSFORM THE ENERGY SECTORS
Electricity 30
W
Today, electricity, heating and transport demands are generally, on the global scale, covered through combustion of fuels and are generally seen as independent. These fuels have a number of environmental, social and economic consequences, such as climate change, pollution of water, soil and air, resource depletion etc., and it seems obvious that this is not a sustainable path to continue on. The reduction of fuel consumption is important whether it is fossil or bio fuels. Fossil fuels have their issues, where carbon emissions is the biggest, but there are also issues in relation to bioenergy consumption. Bioenergy is a limited resource, and even though there is some discussion on how much of this potential can be used for energy purposes in a sustainable way, there is a general consensus on the fact that the resources are not enough to replace today’s consumption of fossil fuels one- to-one. So on the long term we should strive to reduce the fuel consumption of all energy sectors. Fuel 133 40 33 60 Power plant
Figure 1. A traditional energy system where sectors are divided and al l demands covered through the use of fuel.
60
Power plant
Fuel boiler
Fuel 133
Heat 40
40
40
Transport (30)
33
Electricity 30 Figure 2. A combined heat and power (CHP) system that couples the heat and electricity sectors, where 25% of the total electricity demand can be covered by fluctuating renewables.
Electricity 30
Wind
Wind (25%) 8
Electricity 30
Wind (50%) 19
Electricity 30
8
22
60
Power plant
19
22
Fuel boiler
Heat pump
22
25
Fuel boiler
Fuel 133
Heat 40
Fu 10
Fuel boiler
Heat 40
Fuel 100
Heat 40
Fuel 71
Heat 40
CHP
CHP
40
40
15
40
18
45
38
Transport (30)
Transport (30)
Transport (30)
Transport (30)
33
33
33
DEMONSTRATING ONE POSSIBLE TRANSFORMATION PATH
Electricity
Conversion unit
Supply / demand
Heat 40 Figure 3. An integrated energy system where the heat and electricity sectors are coupled through both CHP and heat pumps, and where 50% of the total electr ici ty demand can be covered by fluctuating renewables. Electricity 30 40 Heat 40 Electricity 30 Heat pump 8 25 15
Wind (50%) 19 Wind (25%) 8 Wind (75%) 39
Electricity 30
Win
Electricity 30
Electricity 30
Wind (50%) 19
22
8
In this article, I would like to demonstrate the idea of how a gradual replacement of the energy conversion infrastructure, from the traditional single-sector technology to a multi-sector focus, can help the coupling of sectors and significantly improve the system’s ability to integrate fluctuating renewables reducing fuel consumption. I use four simple illustrations of energy systems, each with the same demands but with different supply systems and primary energy input. Even though the figures are simple, the different efficiencies and the systems’ abilities to integrate fluctuating renewables are based on thorough investigations, and the systems have been analysed using real demand and production profiles in the hourly simulation model EnergyPLAN. Fuel 133 40 33 60 Power plant Wind (50%) 19 19 CHP Fuel 71 38 19 Conversion unit
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22
Fuel boiler
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13
Heat pump
H at pump
22
25
29
Fuel boiler
Fuel 100
Heat 40
CHP
F
Fuel 71
Heat 40
Fuel 39
Heat 40
18
45
CHP
CHP
15
38
11
27
4
8
Transport (30)
Transport (30)
Transport (30)
33 Fuel synthesis 33
Transport (30)
Transport (30)
12
33
16
Electricity
Conversion unit Heating
Supply / demand
Heat 40 Figure 4. A smart ene gy system where the transport sector is coupled to the el ctricity sector through electric vehicles and synthetic fuels, and where 75% of the total electricity demand can be covered by fluctuating renewables. Electricity 30 Heat pump 8 25 15 Supply / demand Electricity
Fuel
Wind (75%) 39
Electricity 30
10
13
Heat pump
29
Fuel 39
Heat 40
Fuel 71
CHP
CHP
11
27
38
Energy efficiency measures in buildings, industry and vehicles are not discussed in this article, but are important to consider in the planning of this transformation. Essentially, reducing the
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Fuel synthesis
Transport (30)
Transport (30)
12
33
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