By Jyrki Leppanen, Naps Systems, Finland

Renewable energies such as solar power are by nature intermittent energy sources. Other technologies can supplement solar energy systems, however, producing hybrid systems that combine the advantages of each technology.

Solar-fuel cell hybrid systems are scalable and clean, making them ideal for small-scale load applications

Solar technologies are the only few technologies that can provide energy with almost maintenance free systems like solar electric systems. Solar electric systems have been used cost-effectively in powering small remote off-grid autonomous applications world-wide. There have also been some large central solar electricity station demonstrations.

Solar electric systems installed in buildings have attracted global attention. There is a growing consensus th.at distributed solar electric systems integrated into buildings, as opposed to large central systems, will be the way to utilize solar electricity in the future.


Solar-fuel cell hybrid systems are scalable and clean, making them ideal for small scale load applications.
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Solar thermal is a more conventional technology than solar electricity. In many cases solar thermal systems can provide most of the hot water and a portion of the heating demand for buildings on an economic basis.

Generator models

However, in Scandinavia the seasonal variations limit the use of solar systems to small applications. In high latitudes the solar electric systems thus need a complementary back-up energy source, which typically is a diesel generator. For residential applications, however, the diesel generators or another type of mechanical energy production equipment is not attractive because of noise, vibrations and pollution related to them and because they are not scalable to smaller units.

However, recent development in fuel cell technology has brought a new back-up possibility closer to reality. Fuel cell systems producing both heat and electricity are soundless, scalable, low emitters (depending on the fuel), high efficiency, vibration free and thus suited to residential applications and for quite small buildings, even family houses.

Small-scale combined heat and power (CHP) generation allows a more efficient way of using primary energy by broadening the applicable area of combined heat and power production to cover small heat loads like family homes. This produces a large number of small power generation devices, quite different in scale from today’s electricity generation business.


In Scandinavia the seasonal variations limit the use of solar systems
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District heating is already widely used in Scandinavia, especially in Finland and Sweden, and for environmental reasons it should be the main trend whenever possible. However, in sparsely populated areas district heating is not economically realistic, thus the only efficient possibility is distributed cogeneration of energy, micro-CHP.

Hybrid solution

The new energy solution here is to combine these new technologies into one total system where they supplement each other. New buildings will consume energy for heating purposes only during winter. During the summer energy is needed only for daily hot water, air conditioning as well as for electrical appliances. The main portion of that energy can be produced by solar thermal and solar electric systems. If the heating system is done with a water based floor heating system that typically needs low circulating water temperatures, the efficiency of the solar thermal system is increased.

During the winter when solar energy prod.uction is minimal in high latitudes and the heating energy demand is at its maximum, a fuel cell based micro-CHP system can produce both the heat and electricity. The most attractive fuels for the micro-CHP system are natural gas or biogas, if there is pipeline network around, but also liquid fuels like methanol or ethanol could be used. In the future there is no need for bringing any additional fuel to the site. During summer the solar energy is stored into hydrogen by water splitting electrolysis powered by solar electricity.

Demonstration

Objectives of the project are to demonstrate new paths to sustainability in building construction in general and to increase knowledge of environmental issues in order to encourage local inhabitants to live in ways that are as environmentally-efficient as possible. The concrete goal is to use a maximum 50 per cent of energy compared to conventional energy use in a similar building and to test new energy efficiency technology for the first time in a commercial building.

Glashusett got its name from the double-skin glass facade. It is a building on three floors located in the Hammarby-Sjöstad area of Stockholm in Sweden. On the ground floor the public will be informed about environmental issues by exhibitions. There is a conference room on the middle floor, while the top floor holds technical installations, a room for group activities and a kitchenette.

GlashusEtt was built with environmentally friendly materials and it is filled with state-of-the art building automation technology. The house is heated by waste heat from the electricity supply substation and the local waste-water pump station, which are both located under the building. The intelligent double-skin glass facade will decrease the need for artificial light and will halve the use of energy for heating, cooling and ventilation. At the same time, the indoor climate will be improved. The energy-saving lighting adjusts the lighting according to the intensity of daylight and the activities in the rooms.

Implementation

Solar modules were installed on the building’s roof to complement a fuel cell system that can operate on biogas or hydrogen generated by solar electricity. When the fuel cell is operating with the biogas the solar electricity is fed into the building’s own electricity grid or hydrogen is produced directly from solar electricity and the gas is put into gas storage. A biogas boiler will cover heating peak loads and in the kitchenette, a biogas stove will be installed. All the gas installations will use biogas produced in the local sewage treatment plant.

The solar electricity goes either to the house’s own grid or the electrolyser, which produces hydrogen to be used in the fuel cell. The water needed in the electrolyser unit could be collected from the rainwater or from the fuel cell. Now, however, tap water is used.

When the hydrogen gas storage is empty the fuel cell unit can utilize bio-produced methane. This biogas enters first the reformer unit and the hydrogen-rich gas then goes to the fuel cell unit. The fuel cell unit will produce 4 kW electricity and approximately the same amount of heat. The generated heat will be used in the building’s heating system while the generated electricity will be used in the building or be delivered to the grid.

Equipment

  • Solar electricity system of 3 kWp with grid-connected inverters and the possibility of direct connection to the electrolyser.
  • A PEM fuel cell system equipped with reformer and a state-of-the-art control system, fuel cell stack power 5 kW, biogas or hydrogen as fuel.
  • A PEM electrolyser unit.
  • Hydrogen gas storage.

Companies involved in the project include Birka Energi AB, which will co-ordinate the project. Financing will be made available by City of Stockholm and the Ministry of Trade and Finance of Sweden. Technical consulting and supply of fuel cell and solar electricity system will be undertaken by Naps Systems Oy. The manufacturer of the fuel cells is H Power.

Naps systems

Further development on these technologies is being done. Naps’ current development focuses on autonomous hydrogen systems based on electrolysers and fuel cells, which offer totally new back-up solutions for low power loads in high latitudes.

For industrial applications fuel cells are already a commercially and economically viable solution. A good example is the fuel cell UPS system based on Hcore500 fuel cell and Naps Seasonal Back-up Unit suitable for telecommunications stations, data centres, banks, air traffic control centres and all industrial applications where high reliability is desired.

Both the fuel cell and solar technologies are by nature modular and low maintenance equipment, although fuel cells need little bit more time to mature technically to the same level than solar electric systems that really do not have any moving parts. Both technologies have positive environmental impact by reducing CO2 and especially NOx and SOx emissions. However, fuel cells will be totally emissions-less only when the fuel cell is hydrogen produced from renewable energies.

The modularity and scaleability of both technologies make it possible to bring these technologies to the single residential house level offering also totally new competitive approaches in energy sector. These technologies are at their best in the low power range when the transmission cost can be avoided and where the private customers pay the highest electricity price today and competitive technologies are not real.ly attractive at all.

The amount of solar electric systems in buildings has increased dramatically during last few years, thanks to forward looking governments that can see their importance. The aim of this is to increase the market size so that production volumes increase leading to cost reduction.

Fuel cells themselves have developed dramatically during recent years through higher power densities, longer lifetime and also lower costs. However, mass production is needed to reduce the price to a suitable level for large-scale energy production with micro-CHP systems. The technical challenge is now on the fuel processor technology; to reduce the size and cost.

It is estimated by different developers and manufacturers as well as by consultants in energy sectors that in 2006-2008 the fuel cell based micro-CHP market will boom in Europe. Different heating equipment companies and energy companies are taking this seriously as can be seen by their investments in development work and the numerous demonstrations going on in Europe.

Further development on these technologies is being done by Naps. Naps’ current development focuses on autonomous hydrogen systems based on electrolysers and fuel cells, which offer totally new back-up solutions for low power loads in high latitudes.