Energy Consumption

Universally, the use of innovative renewable energy is considered of critical importance to environmentally friendly design.  Iceland is in a unique location in that the bulk of the electricity produced here is derived from hydropower plants, which utilize the very renewable resource of water’s flow due to gravity.  Similarly, most of the energy used for heating domestic buildings is geothermal, a renewable resource wherein warm water is issued up from the Earth due to our location on the volcanically active border of two tectonic plates.

However, electricity consumption per capita is among the highest in the world.  This is mostly due to energy-intensive heavy industry, but general household consumption is also very high.  Can we do anything to conserve energy?  Yes, by utilizing local energy resources, we can draw less from the national energy infrastructure.  That some people grow wealthier from energy waste does not justify it, so energy saving considerations guided the design of all systems in Sesseljuhus.

All energy used in Sesseljuhus is obtained from renewable energy resources.  The electricity is from hydroelectric sources, thermal generators and solar panels while the thermal energy comes from the hot water in Solheimar.  All energy used and produced by Sesseljuhus is measured and compiled into an on-going record system.  A display in the lobby allows guests to easily see, even without background knowledge, the real time energy usage and production rates for the building.  The next addition to the energy park of Sesseljuhus will be a hydropower paddle wheel.

Annual consumption of energy in the world is more than 1 x 1014 kWh.  The main energy sources are oil (40%), coal (23.3%) and gas (22.5%).  Energy from hydropower plants only accounts for 7% and nuclear plants produce 6.5%.  Much less comes from other sources, with geothermal, wind and solar only accounting for 0.7%.  In Iceland, however, 70% of the total energy comes from renewable resources and 30% from oil and coal.

The U.S. Department of Energy believes that mankind’s energy demand will increase by 59% over the next 20 years.  Unfortunately, along with this increase will come an estimated jump from 5.8 billion tons of carbon dioxide emissions to 9.8 billion tons by 2020.


Heating buildings requires a lot of energy, at least in the northern hemisphere.  In Iceland, geothermal energy is used both for heating buildings and to produce electricity.  About 90% of Icelanders have access to hot water for heating and electricity.  A quarter of all energy consumption in Iceland is for space heating.  If other energy sources besides geothermal were used for space heating, Iceland would have much more of a problem with pollution than we do today.

Solheimar has its own borehole to get hot water for geothermal space heating and for hot tap water.  Sesseljuhus is included in this system with the hot water being used in a traditional radiant heat system as well as an under-floor heating system.  There was no reason not to use the available resource we are lucky enough to have, so geothermal was gladly incorporated into the design of Sesseljuhus.  To minimize heat loss, the building is well insulated and the windows are all made with high insulation glass from Íspan.

When designing the heating system for Sesseljuhus, the goal was to utilize geothermal heating as much as possible.  The hot water temperature comes in at a high temperature and is sequentially stepped down for various purposes.  In each phase, the water is taken at a certain temperature and returned to the system at a lower temperature after the heat is used.  Heat from the hot water is used in the generation of electricity, in tap water, for heating the air in the ventilation system and for space heating with both radiators and the under-floor system.  Pipes conducted beneath the entrance path outside also keep the approach free of snow and ice.

The radiators in Sesseljuhus were manufactured by Ofnasmiðju of Reykjavik and all pipes and connectors used within the building are from the Tengi company.

Solar Power

The energy transported to the Earth from the sun in one hour could satisfy the total annual energy requirements of all mankind.  The energy in sunlight is actually the source of most other energy resources on Earth.  Solar energy is the driving force behind weather systems, so wind and water power sources depend on the sun.  The same goes for the energy formed through the burning of trees and biomass because ecosystems rely on the sun for plants to perform photosynthesis.  Oil, coal and gas are also indirect products of the energy of the sun since they result from the breakdown of plants over millions of years.

Solar cells convert sunlight into electrical energy by way of a semiconducting material, usually silicon, which absorbs about half the energy of the light that falls on it.  This absorbed energy knocks loose electrons that can then move around to generate an electric current.  By placing metal contacts on the top and bottom of each cell, electricity can be transferred out of the cell to be utilized elsewhere.

Understandably, solar cells produce no electricity when they are not exposed to sunlight.  No electricity is generated when it is dark.  In northern Europe, experience has shown that full performance is only achieved around 10% of the time in an average year and Iceland can usually expect a slightly lower optimum utilization rate of 9%.

Sesseljuhus boasts the largest solar cell array in Iceland with 16 solar cells, each capable of generating 140 W for a total of 2.24 kW.  Based on the utilization rate of 9% of full capacity, the array should annually produce:

9% x 365 days/year x 24 hours/day x 2.24 kW = 1766 kWh

To help understand this figure, the fridge in Sesseljuhus consumes 142 kWh per year (according to the manufacturer).  The annual production of the solar cell array could thus provide enough electricity to power 12 of these appliances each year.


Thermal Generators

Sesseljuhus also has another special device to produce electricity.  The Icelandic company Varmaraf has developed thermal generators that use the heat exchange between hot and cold water to create electricity.  It is not a new concept, but these Icelandic thermal generators have achieved better performance in operation than others that exist.  Thermal generators are not complicated devices, but they require good design.  Efficiency is roughly proportional to the difference in temperature between the hot and cold water sides of the generator.  With a 70o C differential, the efficiency is 3%.

Thermal generators have been used for various specific purposes, including the powering of devices on glaciers and in other places far from human settlement.  The most well-known use of thermal generators was by the astronauts who explored the outer limits of the solar system.  There is not enough sun to benefit from a solar generator in space, so instead thermal generators took advantage of radioactive materials to create the hot side for the devices and the emptiness of space itself supplied the cold side.

Thermal generators are an interesting innovation in the areas of improving energy efficiency and environmental protection.  Many available heat sources can be found in nature and many manmade devices also generate much wasted heat.  Within the thermal generators, geothermal water cools down and the engines are kept cool with containers of fresh or sea water as well as heat exchangers.  There is much energy that could be harnessed from the use of these devices.

In Iceland, thermal generators are widely applicable as geothermal heat sources are widely available.  They are also ideal for the production of electricity using the waste heat from engines.  Thermal generators are preferable to solar generators in Iceland since they can produce electricity continuously and with the same efficiency, whether or not there is sunlight or it is raining.  Even in situations where thermal generators are powered by purchased hot water, they are a more cost effective option than solar generators.





Sólheimar sjálfbært samfélag | 801 selfoss | Iceland | Sími: 422 6000 |