People of Iceland and very lucky to live on geothermal area and they are also very smart to know how to use it to their advantage. One of such usages is geothermal power-plant, where they use steam, coming from the underground to produce electricity. But that's not all, they also use this steam to heat the water, so not only that they have cheap electricity, but also cheap hot water and therefore heating (no need for boilers, central heating with expensive gas or oil ...).

Hellisheidi power-plant in the dusk

Geothermal power-plant Hellisheidi is the biggest of its kind in the world and it provides electricity for about 3⁄4 of Reykjavik's inhabitants. How exactly does it work and what are its limitations were our main interest, so we payed a visit at the power-plant itself.

And here is what we learned there:

This picture shows water circle in Iceland: rain and snow brings water on the ground and it slowly permeates through the soil, sand and rocks. Part of this water stops in the upper levels - that's groundwater, but part of the water travels deeper and reaches the layers of hot rocks (heated by the magma beneath them). This water gets overheated (meaning that the temperature is over 100°C but the water is still in liquid state due to the high pressure in that layer).
Geothermal power-plant pumps water from both layers; groundwater is used for drinking while overheated water is used for heating and electricity production.

Now this picture shows how exactly is the water used in Hellisheidi power-plant. I will try to explain it to you here:

Let's start at the upper pump (shown as sort of a dome on the upper left part of the picture). Here the hot water (purple colour) is being pumped from depths. Steam that comes with the water is partially released in the air to avoid too high pressure and potential threat of explosions - that's why you can see so much steam around the power-plant. The other part of the steam (yellow colour) is used for running the turbines and producing electricity. The hot water (orange colour) is being cleaned and then sent to the city into the heating systems of the houses.

Now let's have a look at the bottom pump (bottom left on the picture, encircled with red lines): this is where cold groundwater is being pumped. Part of this water is send directly to the city into the taps - that's the cold tap water. The other part of groundwater is heated by hot water from the first pump via heat exchanger and then sent at the temperature around 85°C to the city - that is hot tap water.

You can note also also green colour on the picture above. This is the water that is returned back to the ground. You have to understand that to use geothermal energy in the way they do, they urgently need water. And for that reason geothermal power-plant returns some water back to the Earth to ensure that they won't run our of it any time soon. Clever, right?

Model of a turbine

A real turbine

Few interesting facts that we heard:

Here you can see the thickness of the isolation in the pipe

Tips for visiting the geothermal power-plant Hellisheidi:
exhibition with guided tours is open every day between 9am and 5pm, the tour itself is only about 15 minutes long and then you have free time to explore it. Price however is quite high in our opinion - 1450 ISK (about 12€).
Where to find it: if driving from Reykjavik towards Hveragerdi on route 1, power-plant will be on your right, about half way between both cities. And the coordinates are: 64°02'14''N, 21°24'03''W