Active solar heating Water

Heating DHW with solar energy in a high-performance house is sensible. In such houses, the energy needed to heat domestic water can equal or even exceed the energy needed for space heating since the latter has been so far reduced by insulation and heat recovery. Furthermore, demand for heating domestic water is a 12-month energy demand, including the high insolation summer months. Using a solar system is therefore an effective way of reducing the total primary energy demand. Increasingly, the...

Fuel cells

Karsten Voss, Benoit Sicre and Andreas Buhring 12.6.1 Concept Fuel cells, like batteries, are electrochemical power sources. Whereas batteries store energy, fuel cells transform energy. A fuel cell steadily supplied with fuel generates electricity. The fuel can be virtually any chemical substance containing hydrogen. When hydrogen alone is not readily available as a fuel, it can be produced from substances such as natural gas, oil or methanol by a process called 'reforming'. Reforming, however,...

Types of systems

In atmospheric boilers, fuel (oil or gas) is burned under atmospheric pressure. For oil, this results in an inhomogeneous fuel-air mix, varying flame temperatures and the formation of carbon monoxide (CO) and volatile organic compounds (VOCs) harmful to man and the environment. Unburned fuel adds to this. Atmospheric burning gas boilers, however, have very low emissions. They are still common because of their technical simplicity, high reliability and good fuel utilization ratios up to 90 per...

Primary Energy and CO2 Conversion Factors

The delivered and used energy in buildings for heating and DHW is conventionally fossil fuels (gas and oil), district heating, electricity or renewable resources that cause different CO2 emissions when converted to heat. To judge the different environmental impacts of buildings during operation, two indicators are used in this book 1 The primary energy this is the amount of energy consumption on site, plus losses that occur in the transformation, distribution and extraction of energy. 2 CO2...

Opaque building envelope

Hans Erhorn and Johann Reiss 9.1.1 Concept Typically, 50 per cent to 75 per cent of the heat losses of conventional buildings results from transmission losses through the building envelope. These losses can be drastically reduced - for example, in Germany a 50 per cent reduction has been achieved since 1970. This reduction has been halved again by high-performance houses. The transmission losses of a typical house (with 1.5 to 2.0 m2 of building envelope per m2 heated floor area) can be...

Figures

1.1 Single family house in Thening 2 1.2 Installation of a vacuum-insulated roof panel 3 1.3 A compact heating system 5 1.4 A solar water storage 'tank in tank' 6 1.5 Wall section of the row houses in Lindas 7 1.2.1 U-values of the building envelope components 12 2.1.1 Twenty terrace houses in four rows solar collectors on the roof 15 2.1.5 View from the south 17 2.2.1 Energy supply for domestic hot water (DHW), space heating and ventilation 18 2.2.3 Windows in the end wall 20 2.2.4 U-values of...

Photovoltaic systems

Karsten Voss and Christian Reise 14.1.1 Concept High-performance houses need very little heat, but a considerable amount of electricity, which is all the more significant when considered in primary energy terms. In this chapter, we assume that 1 kWh of heat from natural gas requires 1.14 kWh of primary energy, while 1 kWh of electricity requires 2.35 kWh of primary energy to produce. For this reason, it is highly attractive to consider ways of producing electricity from a renewable source,...