The old oil-fired and electrical boilers used for heating homes really are past their sell-by dates – both from an environmental point of view and in light of the rising fuel prices. Some households have gone over to heating systems based on renewable energy, or have linked up to district heating networks. What may a smart future heating system look like? The answer depends on the technical properties of individual buildings and how much a householder is prepared to invest. Most people also want straightforward, reliable heating systems.
There are a number of Swedish manufacturers of heating systems who offer products which are energy-efficient and use renewable energy. They have products which provide environmental benefits. Here we are taking a closer look at the products offered by NIBE, a company based in the province of Småland.
Geothermal heat pumps
A heat pump draws heat from the surrounding air, ground or bedrock, or from a lake. The temperature of the earth’s crust rises by an average of 1°C for every thirty metres of depth, but to access geothermal energy, drilling to extreme depths is required. The boreholes used by domestic heat pumps utilise energy generated by the sun. To heat a house, the heat has to be collected, and a heat pump used to turn it into useable heat. A house which consumes approximately 30,000 kWh/year for heating and hot water can save up to 2/3 of its consumption by installing a geothermal or ground heat pump. If all single-family houses in the Nordic region were fitted with a heat pump, the total energy consumption for these houses would fall by more than 40 percent. Unlike biofuel and district heating, heat pumps do not use combustion or other energy to generate heat. According to Nibe, nitrogen oxide emissions are, therefore, reduced by almost 30 percent, hydrocarbon emissions by 80 percent and carbon dioxide emissions by 36 percent from a single-family house. Since electricity is required to run the pumps which collect the heat, geothermal technology is not, however, completely without impact on the environment.
Exhaust air heat pumps
All buildings must be ventilated, and unfortunately, heat is released with the exhaust air. We are, quite literally, heating the atmosphere. But an exhaust air heat pump recovers the heat energy in the used air, and this can then be used to heat water and the building itself. This is how it works: a fan extracts the ventilation air from, say, a wet area, kitchen and bedroom in a house. The extraction points are arranged in such a way that the whole house is ventilated. New outside air enters through vents in the outer walls, and this ensures that all the rooms in the house are ventilated.
Wood and pellets
Swedes have always used biofuels for heating their houses. 100 years ago, burning wood in kitchen stoves, fireplaces and wood-fired boilers to generate heat was part of most people’s everyday lives. The wood-fires boilers have survived, but have been improved to be more energy-efficient and less damaging to the environment. Their efficiency can now be as high as 90 percent, and natural ventilation and fans can be used to stabilise the combustion process. Modern wood boilers are often used in combination with a 1,000-2,000 litre accumulator tank, which allows the heat to be distributed over time.
Pellets are made from sawdust and wood shavings from sawmills, the furniture industry and other wood product industries. The raw material is dried and subjected to high pressure to form small, round sticks 6-8 mm in diameter and 10-12 mm long. The use of pellets can reduce the cost of heating significantly, compared with oil and electricity at today’s prices. The boilers are automatic and a screw feeds the pellets from a storage bay to the boiler. Hot air from an ignition element and a fan ignites the fuel. When the temperature in the boiler falls to a certain level, more pellets are added and the burner ignites once again.
Fireplace heating stoves carrying the Swan environmental label
An open fire can make a room feel lovely and cosy, but unfortunately, most of the heat disappears up the chimney. In addition, a large quantity of indoor air, which you have paid a lot of money to heat, also disappears the same way. A modern fireplace heating stove is a much better option from an energy-saving point of view. A fireplace heating stove gives the same cosy atmosphere, but also helps to improve the heating economy of the home.
Small-scale burning of wood does, however, cause problems to the environment. The emission of particles containing harmful polyaromatic hydrocarbons (PAH), for example, must be kept to a minimum. It is, therefore, important to ensure that a fireplace heating stove is efficient and does not emit incomplete combustion products of hydrocarbons.
The company, Nibe, decided to obtain Swan labelling for its fireplace heating stoves, to demonstrate that the products were of a good environmental standard. To obtain Swan labelling, a fireplace heating stove must comply with certain standards in several areas, including:
- Emission of hazardous substances: carbon dioxide, polyaromatic hydrocarbon and particle emissions.
- Energy efficiency: the fireplace heating stove must have an efficient combustion process and a high proportion of the energy stored in the fuel must be dispersed into the house in the form of heat.
- Constituent materials: requirements regarding environmentally-hazardous materials, such as heavy metals, external flame retardants and phthalates.
- Operation: fireplace heating stoves must have clear installation and maintenance instructions, and must be tested in accordance with, and pass, stringent quality and operating requirements.
This article was first published in Advantage Environment printed in February 2008