The energy sector

The energy sector is the sector with the largest emissions of greenhouse gases (35% of total emissions in 2010, see Greenhouse Gas Emissions). Of these emissions, 25% are related to electricity generation used by other sectors. A large part of the electricity production is done at power plants that use fossil fuels (coal and natural gas). The IEA has an overview, [L55] (see Figure "Electricity generation by fuel and scenario, 2018-2040") of the various technologies used in power generation in 2018:

The figures are given in petawatt hours. 1 PWh = 1 000 000 000 000 kWh.

A survey by the IPCC [L54] shows how much CO₂ that is emitted from different types of power plants. This is a so-called life-cycle survey that takes into account emissions in the construction phase etc., in addition to those during the actual production. Emissions of CO₂ are measured in grams of CO₂ equivalents per kWh produced. The results are shown in the table below:

Coal:	820
Natural gas:	490
Coal with carbon capture (CCS):	220
Solar cells:	48
Hydropower:	24
Wind power:	12
Nuclear power:	12

These figures show that there is great potential for reducing emissions by switching to other forms of production than coal and natural gas.

Electricity generation and synchronised power grids

Most major power plants in the world are interconnected in synchronised power grids that use alternating current (AC) with the same frequency (for example, 50 Hz). Norway belongs to a Scandinavian grid [L58] whereas most of the other European countries are interconnected in a separate network (a good overview of such power networks can be found in a Wikipedia article [L59]). Such networks must always have a balance between production and consumption. This is regulated in different ways. Small short-term variations in consumption are regulated by using tiny frequency regulations in the power grid as a signal to the power plants to decrease or increase production to match the consumption changes (so-called droop speed control [L60]). If major changes in consumption occur, such as daily variations, a larger change in production must be effectuated. Then it is important that the grid includes types of power plants where such changes are possible. Hydropower plants are ideal in this context, since the water pressure can easily be adjusted up and down.

Power plants connected to a grid must fit among the mix of power plants connected to the same grid. For example, you cannot have a power grid that is only based on wind power, because you would have a problem on windless days. The way different types of power plants fit into an existing power grid is therefore important, in addition to the cost and the benefits and disadvantages of the type of power plant itself.

Costs

Estimating the cost of using different types of power plants is a challenging task. There are many ways to do this. A calculation method that seems to be widely used is the Levelised Cost of Electricity (LCOE). This includes life cycle costs that cover investments and running costs over the plant's operating period. Costs are converted to a present value based on a given interest rate, and are stated in US dollars per produced kilowatt hour ($/kWh), or megawatt hour ($/MWh).

The cost of using renewable energy sources, such as wind and solar power, has dropped significantly during the last 10-year period. This is shown in a report [L66] from 2019 published by the International Renewable Energy Agency (IRENA) [L65]. According to an article in the magazine Forbes from 2017 [L56], these sources now cost less than, or are on a par with, coal power. I have put the figures from IRENA and Forbes together in the following illustration which shows how the cost of different types of energy sources have evolved from 2010 to 2018:

CSP stands for Concentrating Solar Power and represents a type of power plant where the sun's rays are concentrated by means of mirrors to a small area that constitutes the heat source in the power production.

The costs in the above illustration do not include costs for upgrading the mains as a consequence of connecting new power plants to the grid. Such costs vary depending on the type of the new power plant. Solar and wind power result in unstable power production and this requires greater transmission capacity in the grid to cope with production peaks. Furthermore, it may be necessary to invest in other power plants where electricity production can be more easily regulated to cover missing production from sun and wind. Such extra costs will vary greatly between various power grids. Where there are already many power plants that can easily regulate production up and down, such missing production will not be a problem. The IPCC estimates the costs associated with such extra investments in the power grid to be between 1 and 32 $/MWh [L67].

Area requirements

The area a power plant occupies will vary greatly depending on the type of power plant. Land-based wind power requires quite a large area, but it can often be used for other purposes as well, such as agriculture. Coal and nuclear power require smaller areas. The table below shows the capacity density for different tpes of power plant. This is a figure that indicates how much power can be produced per unit area. The figures are taken from various sources (given in column 3 of the table).

Power Plant Type	Capacity density (MW/km²)	Source
Biomass	0.5	[L68]
Wind power	4.1	[L68]
Solar Power CSP	25.0	[L142]
Solar cells	31.2	[L142]
Coal power	361.0	[L69]
Conventional nuclear power	386.0	[L68]
NuScale reactor	2778.0	[L68]

Latest update: 2021-07-21