Nine cubic meters of coal or a handful of uranium are enough to cover the one-year energy demand of an average Finn. Different fuels store energy in different ways.

Different energy sources hold different amounts of energy in them. In addition, the energy in them can be in many forms. Wind has kinetic energy, the sun radiates energy in the form of light and heat, wood and fossil fuels have chemical energy that can be released by burning them, and in the nucleus of atoms there is nuclear energy, which can be released (mostly as heat) by splitting a heavy atom (like uranium) in fission or combining light atoms in a fusion (hydrogen). 

But how much of this energy is packed in a given amount of a fuel? How many joules or watt-hours are there stored in wood, oil, coal or uranium per litre? The differences are astonishing. 

A Finn consumes a rather high amount of energy, around 185 kilowatt hours (kWh) every day, when the national total is evened out for each of us. This means that on average, a Finn uses energy at a constant power of roughly 8 kilowatts. This is about the same as each of us having a sauna stove or a set of cooking stoves on, at full power, all the time. A personal Tesla Powerwall 2.0, at 14 kWh, would be empty in less than two hours. Our relatively high energy use is due to a couple reasons: The climate in Finland is cold and we have quite a bit of energy intensive industry. In addition, average distances are long, increasing transportation fuel use. 

Our daily portion of energy 

The Finns use a lot of different energy sources. We use a bit over a gallon’s worth of oil (about 43 kWh), of which most (55 %) is used in transportation. Wood and forest industry by-products and waste streams could fit in a large basket as fuelwood (about 48 kWh). In addition, we use a bag of coal (18 kWh) and around 1000 litres of natural gas (about 10 kWh). Hydro and peat account for around 8 kWh each, and we import a similar amount as electricity from our neighbours (9 kWh, mostly from Sweden). Wind is consumed at 2 kWh and other energy sources account for 7 kWh. We also use about a grain of sand worth of uranium (34 kWh). 

The scales of energy density

It is a bit problematic to compare energy sources and fuels between each other, since they are different and can be used in different situations. Gasoline is great for cars with internal combustion engines, while it is worthwhile to build electricity transmission and district heating networks to most houses and apartment buildings. But if we assume that various energy sources could replace one another on a one-to-one basis (although I don’t recommend stuffing firewood to a car’s gasoline tank), we can compare the energy densities of each energy source and fuel in a relatively concrete manner. 

A Finn consumes 185 kWh of energy per day, 67 megawatt hours (MWh) per year and if we live to be 80, on average 5,400 MWh during our lifetimes. The following table presents this energy produced from each fuel completely, in litres.

Fuel Litres / day Litres / year Litres / lifetime
Oil 20 7300 584000
Coal 25 9125 730000
Wood 90 32850 2628000
Peat 200 73000 5840000
Uranium in Breeder reactor 0.0000004 0.00016 0.013
Uranium in current reactors (light water) 0.00004 0.016 1.26
Granite (with 2,8 ppm of uranium on average) 0.15 56.38 4510

 

What about energy sources without fuel?

Hydro, wind and solar power don’t use fuel, but harness the energy flows in our environment. We can still make some comparisons on their densities and scales. Let’s assume electricity replaces other energy one-to-one. Often electricity is more useful than other energy carriers (except in vehicles which usually need liquid fuels), so this can be seen as a rather conservative comparison. On the other hand, we compare annual production and consumption, so we assume that wind and solar production can meet real-time demand without problems (which they normally don’t do).

Kollaja hydro-electric dam project, a topic of a lot of controversy and environmental discussion, would be able to produce the energy for about a thousand Finns (average 8 MW capacity). 

A wind turbine of three MW nameplate capacity (and one MW of average capacity) would supply 150 Finns with their energy needs. 
And if solar power would be transferrable from summer time to the dark and cold days of winter, Finland’s currently (spring 2017) largest solar PV plant, Kivikko, would be able to provide energy for about ten Finns (annual production 700 MWh).

 

Note: There is a slight inconsistency in the article regarding the energy content of wood fuels and peat. The energy content for wood fuels is measured in solid cubic metres, while the energy content for peat is in loose cubic metres. In real world use, peat has often a slightly higher energy content per volume than wood fuels. Measuring and comparing the energy contents of various biofuels like wood and peat is complex, as there are many types of those fuels and their relative moisture content also affects the results greatly.