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Energy prices and the associated operating costs for domestic water and space heating are on a continuous upward trajectory. Investment in systems based on regenerative energies allows for at least a partial decoupling of heat generation costs from increasing oil or gas prices. Decentralised heat generation plants are well suited to the integration of regenerative energies. These can either be coupled with conventional heating systems or used for the generation of heat in their own right. Various different programmes, which are also eligible for use by public institutions, already exist for the subsidisation of investment in regenerative energies. For a comprehensive overview of subsidisation programs please go to: http://www.foerderdatenbank.de/Foerder-DB/Navigation/root.html (German language only).
For new buildings, the following has applied since the coming into force of the Renewable Energies Heat Act (EEWärmeG) on 1 January 2009: a proportion of the heating requirements must be provided by renewable energies. This applies to both residential and non-residential buildings for which a building application or notification of intention to build has been submitted since 1 January 2009. It is up to the owner to decide which renewable energy carriers he intends to employ. How high the proportion of this energy form is of the total heating requirement depends on the energy carrier. In the case of solar heating, at least 15% of the heating requirement must be covered; in the case of solid or liquid biomass this proportion must be at least half of the heating requirement, in the case of gaseous biomass, 30%, and in cases where ambient heat (heat pumps) or geothermal heat are used, at least 50%. However, substitute measures are also possible, such as for example the supply of at least 50% of the requirement with heat from co-generation or waste heat. It is likewise possible to use thermal insulation over and above the standard set by the law to consume up to 15% less primary energy than is demanded by statutory requirements.
Measures for the use of renewable energies in the context of the market incentive programme of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety are subsidised by the Federal Office of Economics and Export Control (BAFA).
Eligible for subsidy are the construction and extension of
Alongside these existing subsidies there is also a bonus system for the combination of renewable energies that can give rise to higher subsidy contributions.
Eligibility for subsidies extends to the following owners, lessees, or tenants of properties in which the system has been installed or where installation is intended:
For further information on the market incentives programme please go to:http://www.bafa.de/bafa/de/energie/erneuerbare_energien/index.html
For the supply of heat from biomass wood pellets, wood chips and logs are the principal fuels of interest. The acquisition costs of a wood-fired heating system are somewhat higher than comparable gas and oil heating systems, although the operating costs are as a rule somewhat lower. Approximately 20,000,000 m³ of wood are used annually in Germany for heating purposes. At over 14,000,000 m³, logs from forestry plantations are the most significant wood fuel. Only large heating stations and co-generation plants are in a position to incinerate scrap wood containing harmful substances, recovered for example from the demolition of houses. For small plants the air pollution control measures required would not be economically sustainable.
Wood-fired heating systems, also known as small heating systems for biomass, come in the form of firing systems for individual rooms, which can be used in addition to standard heating systems. On the other hand, central heating boilers heat entire buildings, along with their drinking water supplies. As is the case with oil and gas heating boilers, these are installed in their own boiler rooms. As far as public bodies are concerned it is only central heating boilers which are of relevance. A directive on small heating systems is in preparation in the context of the Ecodesign Directive (2005/32/EC). For information on this subject and the pilot study please go to:www.ecosolidfuel.org.
In order to operate wood-firing systems in as environmentally-friendly a manner as possible, low-emission and efficient fireplaces should be used with dried wood. Furthermore, regular maintenance and monitoring of the system by specialists is required. Modern systems work with electronic regulating equipment that monitors the combustion process, output and heat distribution.
If possible, systems should be acquired that meet the requirements of stage 2 of the first Ordinance on the Implementation of the Federal Immission Control Act (1. BImSchV) on Small and Medium-Sized Firing Installations. 1. BImSchV contains requirements for the fuels to be used in small systems, limit values for the emission of harmful substances, monitoring specifications and a regulation concerning the refurbishment of existing systems. A revised version of this ordinance came into effect on 22 March 2010. The second limit value stage is significantly stricter than the stage 1 level that applies today and will be mandatory for new systems from 2015. The following table lists the harmful substance limit values for small wood-fired boilers:
| Fuel | Rated heat output [kW] | Dust [g/m³] | CO [g/m³] | |
|---|---|---|---|---|
| Stage 1: Systems installed after the enactment of the ordinance |
Pelletised and non-pelletised wood (logs, saw dust), | ≥ 4 – 500 | 0.1 | 1.0 |
| Wood pellets | ≥ 4 - 500 | 0.06 | 0.8 | |
| Stage 2: Systems installed after 31.12.2014 |
Pelletised and non-pelletised wood (logs, saw dust), wood pellets | ≥ 4 | 0.02 | 0.4 |
It is important that the system be of the correct size, i.e. that it should provide the correct output in kilowatts [kW]. A turndown of the firing system leads to significantly higher emissions. What is particularly problematic here is the situation in which the system is merely sustaining a firebed and is hardly generating any heat. Sufficient buffer storage makes it possible to operate the system at full load, with lower emission intensity, and to store the heat that is not immediately required. In Germany the Federal Immissions Control Act (BImSchV) lays down a requirement for wood-fired boilers with an output of more than 15 kW to have a buffer tank which provides interim storage for the heat released from the wood that cannot be directly taken up by the heating system. Pursuant to BImSchV, the buffer volume must be at least 25 l per kW of boiler output. In practice, however, it should exceed 50 l per kW of boiler output; the BAFA's guidelines for subsidisation require at least 55 l/kW. [CARMEN 2005]
Pursuant to Article 3 paragraph 1 1st BImSchV the following are permissible as wood fuels: Barbecue charcoal, untreated pelletised wood and briquettes from untreated wood, but not, however, chipboard or painted wood.
Wood-fired heating systems require a store room for the fuel which is somewhat larger for woodchips than for pellets. The room should be as dry as possible to prevent mould and decomposition. The water content of the fuel has a great effect on its combustion behaviour. Freshly felled timber contains 45-60% water. This water content decreases after one or two years in optimal drying conditions to 15-20%. The low residual moisture content means that the storage of pellets is less problematic than that of firewood. Logs for burning should be stored in sunny and windy places (for example, in front of south- or west-facing facades) on dry ground. In the process a sufficient ventilation gap of at least 10 cm from the house wall should be ensured. The firewood should also not be in direct contact with the earth as it can always draw moisture out of the soil. If the wood is cross-stacked or stored in pallet cages, this will further aid the drying process. After the summer drying phase the firewood must be protected from rain, for example, by the use of plastic tarpaulins. Split wood dries better and demonstrates better combustion behaviour. If the firewood is bought from a dealer confirmation of the water content should be provided. [Holz&Pellets]
Pellets are compressed, untreated sawdust and wood shavings left over from production processes and scrap wood of a standardised quality. They have been on the market in Germany since 2000. By the end of 2008 more than 105,000 private residences were being heated using wood pellets. Six to eight cubic metres of wood shavings are required to make one tonne of wood pellets. When dry leftover wood is used, approximately 2.7% of the energy content of the produced wood pellets is required for pellet manufacture; when damp industrial or forestry leftover wood is used, the figure is between 3 and 17%. In comparison, the proportion required for the production of fuel oil is 12%. [NRW 2009]
Pellet central heating systems are available with an output of 7 kW. A programmed management system governs the rate at which the pellets are conveyed on a worm conveyor into the combustion chamber. In the case of vacuum conveyer systems the pellet store can be up to 20 metres away; meaning, for example, that it is possible to store the pellets in underground tanks outside the building. The store should be no more than 30 metres straight-line distance from an access road for silo vehicles. A sloping floor in the store will ensure that the worm conveyor picks up all the pellets. The optimum size of the store depends on the annual pellet consumption, which can be calculated using the heating load. The heating load is the output that the boiler must be capable of producing to heat the building at the lowest winter temperature in the range typical for the region. The volume usable for storage is around two-thirds of the volume of the space. Prior to constructing the boiler and store rooms it is advisable to consult the district chimney sweep or the responsible construction supervisory authority in respect of the regulations applicable to storage, combustion air inlet and flue gas evacuation.
A continuous fuel feed and fan-assisted, regulated air intake will guarantee optimal combustion and a constantly high level of efficiency. Modern wood-fired boilers often come equipped with their own built-in flue gas sensors (for example, lambda sensors) which permanently monitor the combustion and optimise and regulate it within certain parameters.
In the case of efficient systems the firing efficiency is more than 90%, meaning that 90% of the input energy is turned into heat. This value has only limited practical relevance because it is usually stated for nominal load operation (=operation under test conditions) and not for the turndown that tends to obtain in real life. Turndown efficiency rates are lower. It is not yet standard practice with wood-fired boilers to state the “normal supply level” which also takes turndown into account. If the efficiency is above 90% at full load and above 88% at 30% part load then the system is particularly efficient.
Combining this system with a solar thermal installation renders it possible, depending on heating requirements, to save up to one-third of the annual fuel requirement. [NRW 2009]
For an overview of wood pellet price trends please go to http://www.carmen-ev.de/dt/energie/pellets/pelletpreise.html#2.
Wood pellet boilers can be awarded the Blue Angel ecolabel on the basis of the RAL-UZ 112 basic award criterion.
Woodchip heating systems are appropriate for larger heating systems such as those used in apartment blocks, schools or indoor swimming pools. Woodchip heating systems, like pellet boilers, are automatically fed. The low fuel price means that they can be more economical to run than pellet heating systems. Woodchips are defined as mechanically shredded leftover forestry wood, smallwood and other low-quality wood pieces of less than 3 cm in size. They have a calorific value of roughly 40 kWh (= 14.4 MJ) per kg (depending on type of wood, at a water content of approx. 20%). The water content, which influences the calorific value, varies in dependence on the type of wood and length of time stored. This has consequences for the heating, the settings of which, depending on the composition of the fuel, may need to be changed. This makes it more costly to operate woodchip heating systems than the pellet equivalent. [CARMEN 2005]
Log-fired boilers are fed manually with logs (at lengths of 30 to 100 centimetres). The filling space of a modern fan-assisted log-fired boiler is sufficient for a combustion time of between four and eight hours. After this the wood has to be restocked. In modern log-fired gasification boilers the individual wood combustion stages - that is, wood gasification and the gas combustion - take place at separate locations and times. The wood is gasified in the firebed and the gases are directed to the side or downward prior to combustion in a separate combustion chamber. The combustion is clean and even. This results in low emissions of harmful substances and greater efficiency. Electronically regulated boilers are equipped with a speed-controlled fan. This uses a lambda sensor to measure the residual oxygen content of the flue gases and subsequently regulates it. Changes in the amount of input combustion air make it possible to a limited extent to regulate the thermal output. The hot flue gas passes over the heat exchanger, thereby surrendering its heat to the heating system. Only then is it evacuated via the flue. Modern boilers achieve firing efficiencies of around 90%. [CARMEN 2005]
In solar heating the radiant energy from the sun is transformed directly into heat energy. 80% of solar heating plants currently generate hot water for domestic use; the rest provide support for hot water and heating systems. Solar heating systems work most effectively in buildings which also require heat in the summer. Buildings which see little use during holidays or at weekends, such as schools, are less suitable for this kind of system.
Solar systems with a collector area of more than 100 m3 require careful adaptation to the consumption profile, which entails individual planning and dimensioning. However, the economies of scale and price reductions achievable by larger collector areas compensate for the increased planning costs. Generation costs for solar heat in large installations are between 8–10 cents/kWh, making them cheaper by a factor of 2 than small-scale installations. [BINE Themeninfo 2008]
For large-scale solar thermal installations, annual maintenance costs are assumed to amount to approx. 1 to 1.5% of the investment costs, which is equivalent to those of conventional boiler systems. At 20 to 25 years the lifetime is longer than the 15 years considered as standard for fossil fuel systems. The operating costs for solar systems merely include electricity to run the pumps and control systems and are therefore low. So, roughly 1 kWh of electrical energy serves to generate about 40 to 50 kW of heat. The pumps only run when radiant heat from the sun hits the panels (maximum 2,000 hours per annum). [BINE Themeninfo 2008]
A collector heats a medium (for example, a water-glycol mixture), which conducts the heat to a storage tank. If the solar heat is also used to support space heating, large-scale systems generally use a two-tank system with a water tank for domestic use and a large tank as a heat buffer for heating. The domestic and buffer tanks are charged with solar heat, whereby the domestic water tank takes priority. The buffer tank is intended to keep the heat generated during the hours of intense sunshine in reserve for times of increased demand. In tall and slim heat reservoirs the water arranges itself in strata of different temperatures, as the lower density of warm water leads it to ascend to the upper part of the tank, whereas cold water remains in the lower part. The warm water is drawn off right at the top of the tank where it is at its warmest, and returned water is fed into the bottom of the solar buffer tank. If insufficient quantities of solar radiation are available in the winter then conventional heating is switched on as soon as the temperature in the upper part of the tank becomes too low. For the purposes of tank dimensioning, systems for domestic water heating should assume a volume of 50 litres per square metre of collector area. [BINE basisEnergie 4]
The quotient derived from usable thermal energy and incident solar energy is the conversion factor or optimal level of efficiency of a solar collector. The value indicates what % of the solar radiation passes through the collector’s transparent cover to be taken up by the absorber.
The thermal loss factor or k-value gives a figure to the heat loss. The k-value is the energy loss from the absorber to the surroundings in W per m² of collector area and that lost due to the difference between ambient and mean absorber temperatures. The higher this temperature difference is and the higher the k-value, the greater the heat loss.
Three types of technology are currently in use in solar thermal applications:
For systems for heating domestic water, standardised planning guidelines are in force. Combined systems for hot water and space heating and systems integrated into heating grids require detailed planning and dimensioning. The layout of large-scale systems requires individual dimensioning. A simple system construction is the best way to achieve high levels of operational reliability.
Prior to planning a solar thermal system the following points require clarification:
Solar collectors can be awarded the Blue Angel eco-label on the basis of the RAL-UZ 73 basic award criterion. A system must fulfil this award criterion if it is to be eligible for subsidisation through the market incentives programme. To receive subsidies the solar collectors furthermore have to carry the European Solar Keymark approval mark.
Solar thermal systems are also suitable for providing air conditioning within buildings. With the aid of solar energy, solar climate control, as it is known, can cool the air and regulate air humidity. Such systems are mostly to be found in non-residential buildings in which large numbers of people gather (for example, office buildings, theatres and sports halls). In this procedure the operating power source of a refrigeration system is solar heat rather than electrical energy from the electricity grid. In comparison to other cooling systems the CO2 emissions are low. A further advantage of cooling with solar heat: Solar irradiation is usually at its strongest at the time of greatest need for air conditioning.
Two types of technology are currently in use: In the closed procedure cold water is used as the operating medium. Open sorption procedures provide cool air with corresponding levels of humidity. Sorption designates the adsorption of a cold medium, such as water, to another material. If this other material is liquid the term used is absorption and, if it is solid, adsorption. The compound can be dissolved again by the introduction of heat. [FVEE 2008]
Heat pumps use the same basic principle as refrigerators. Refrigerators extract heat from the cooling medium via the vaporiser and release it into the surroundings via the condenser at the rear of the appliance A heat pump extracts heat from the surroundings (soil, water, air), brings this up to the temperature of a domestic heating system and feeds it into a heat distribution system (for example, underfloor heating) in a building. The heat pump requires operating energy to raise the temperature; this energy is usually supplied by electricity. Systems deriving operating energy from natural gas are (as yet) uncommon.
Heat pumps for space heating are used either as the sole generator of heat or in combination with a second generator using gas, oil or electricity. This depends on the conditions that obtain in the place where they are used. The second heat generator kicks in if the heat pump can no longer cover the heat load by itself. If the heat pump is the sole source of supply, the term used is monovalent. Monovalent systems are commonplace in houses with low-temperature heating. This requires on the one hand low investment costs and, on the other, an exact calculation of components and the overall system. The integration of a buffer tank into the heating system can compensate for fluctuations in demand for heat and the switch-off times for reduced heat pump electricity tariffs. If low external temperatures require an additional heating system, the term used is “bivalent operation”.
Heat pumps can be used wherever low-temperature heating systems are available to take up the heat. The efficiency of the heat pump increases in line with the reduction in temperature difference between the heat source and the heating system. Groundwater and soil (approx. 80% of market share) have a relatively high and stable mean temperature during the winter when the demand for heat is high. This limits the required rise in temperature and is advantageous for the performance of a heat pump. Connection to a panel heating system (for example, underfloor heating) is favourable for the heat pump. Such systems work with low supply temperature, usually 35 °C. This also reduces the temperature difference that the pump needs to overcome. [BINE basisEnergie 10]
Heat pumps use different technical principles. A distinction is made in terms of function principle between compression and sorption heat pumps.
In the case of the compression heat pump the input of low-temperature heat (from the surrounding air, groundwater, surface water) causes a medium with a low boiling point (cooling medium, HFCs such as R407C or naturally-occurring substances such as R290/propane) to evaporate in a vaporiser and then to be compressed in a compressor (up to 20 bar). The gas thereby warms up and releases its heat to the hot water for heating. In so doing it condenses. The working medium is expanded in a throttle member (capillary tube, expansion valve) and reintroduced into the vaporiser. The compressor is driven by an electric, natural gas or diesel motor. In the case of compression heat pumps driven by combustion engines, the waste heat from engine cooling and, if applicable, exhaust gases can be used as heat energy.
In the case of sorption heat pumps reversible physical-chemical processes are used in which two substances are separated by the introduction of heat and this heat is again released when the two substances are recombined. Often water is used as the solvent and ammoniac as the working medium. In the case of an absorption heat pump the operating energy for the compressor is derived not from a mechanical (mechanical compressor) but from a thermal source. This energy can therefore be provided by the combustion of gas or oil or through the use of waste heat. [BMU 2009]
A heat pump is efficient if the heat extracted from the environment is significantly greater than the primary energy used to drive the heat pump.
The energy efficiency of an electrical heat pump is reflected in the heating seasonal performance factor (HSPF). This represents the ratio determined for one year of the useful heat released for space heating to the required input (operating work including auxiliary energy). In the case of electrical heat pumps this is the required electric current. For example, an HSPF of 3.0 for an electrical heat pump means that 1 kWh of electric current is required to provide 3 kWh of useful heat.
The seasonal performance factor is calculated as follows:
Seasonal performance factor = the sum of useful heat in kWh / the sum of the input operating energy in kWh
The coefficient of performance (COP) on the other hand only provides information on certain operating conditions that are strongly susceptible to fluctuation, particularly in the operation of air/water heat pumps (different temperatures of the external air heat source). It represents the ratio of power input to the useful output. Indicated are only momentary best values of certain operating conditions. This suggests a higher degree of efficiency.
The COP is calculated as follows:
COP = heat output in kW / input electrical power in kW [UBA 2008 heat pumps]
In order to be eligible for subsidisation according to the market incentives plan, electrically driven heat pumps have to demonstrate a seasonal performance factor of at least 4.0 in the case of brine/water and water/water heat pumps in new buildings or at least 3.7 in existing ones; in the case of air/water heat pumps of at least 3.5 in new buildings or 3.3 in existing ones. In the case of gas-engine driven heat pumps, a demonstrable seasonal performance factor of at least 1.2 is required (http://www.bafa.de/bafa/de/energie/erneuerbare_energien/waermepumpen/index.html).
For heat pumps with electrically driven compressors a Blue Angel ecolabel can be awarded on the basis of the basic award criterion RAL-UZ 121, and for adsorption or absorption heat pumps or those with combustion engine-driven compressors a Blue Angel label can be awarded on the basis of the basic award criterion RAL-UZ 118.
TEWI (Total Equivalent Warming Impact) is applied in the assessment of ecological impact of heat pumps. The coefficient describes the climate impact of a system using a CO2 equivalent as reference. It accounts for the direct share of the refrigerant used as well as the indirect proportions of global warming potentials of the propulsion energy. Determination of TEWI limits allows for offsetting refrigerant emissions with a high Global Warming Potential with very low energy use emissions (high-efficiency installations) and vice versa. SPF and GWP as well as refrigerant volume are used as system-specific factors to determine the TEWI coefficient.
The TEWI coefficient is calculated using the following formula:
TEWI = GWP * (ER * n * m + αV * m) + n * β * Q/SPF
Using the following operands:
GWP: Global Warming Potential [-]
ER: Emission rate [%/a]
n: life of system [a]
m: Filling quantity of refrigerant [kg]
αv: Disposal loss [%]
β: Conversion factor [kg CO2/kWh]
Qh: Heat demand [kWh/a]
SPF: Seasonal performance factor [-]
The following parameters are applied:
Heat pumps can also be used as waste water heat pumps. Heat from waste water is an almost entirely unexploited energy source with great development potential. For example, unused energy is lost to households when the waste water goes down the drain. The use of heat pumps and heat exchangers can exploit the heat from domestic waste water to heat buildings or domestic hot water to the desired temperature. In conjunction with heat pumps waste water can for example be used as a source of heat to supply local heating systems or such systems installed in individual buildings. Various different systems available on the market allow treated and untreated water to be used in different ways. What is required, however, are waste water pipes with large and regular throughput.
One end product of burning wood is carbon dioxide (CO2). CO2 is not poisonous but it does contribute to the greenhouse effect. The burning of wood is CO2-neutral as long as only as much wood is burnt as is grown back. In a closed carbon circulation the combustion releases the amount of carbon dioxide (CO2) that the tree absorbed in the process of growth. The plants which subsequently grow fix the carbon dioxide generated by the combustion. However, CO2 is also released in the production, preparation and transport of the wood.
A further end product is dust. The dust consists to more than 90% of particulate matter: particles of less than 10 µm (PM10) in size. These very fine particles penetrate deep into the lungs when breathed in and represent a burden for the whole organism. Consequences can be bronchitis, asthma attacks or strains on the cardio-vascular system. Particulate matter is also suspected of being carcinogenic. Particulate emissions from wood-fired boilers are many times higher than from oil-fired systems. New limit values for wood-fired boilers have been in force since 22.03.2010. Should old wood-fired heating systems exceed the allowable limit once the transitional period has elapsed they must either be retrofitted with a filter or replaced by a modern system.
Wood always contains small quantities of nitrogen, sulphur and chlorine compounds. So when oxidation takes place harmful substances such as nitrous and sulphur oxides arise, as does hydrochloric acid. If the combustion of wood is incomplete, poisonous carbon monoxide and methane can arise. Methane as a greenhouse gas is 21 times more powerful than carbon dioxide. In addition, significant amounts of polycyclic aromatic hydrocarbons (PAH) are also generated (including the carcinogenic benz(a)pyres). If the wood being burnt has been treated with wood preservative or varnish, then highly poisonous dioxins and furans can result. In densely populated areas and valleys, wood-fired heating systems with their low chimneys can have negative effects on air quality and be a nuisance to neighbours. [UBA 2007 Holz]
In the case of plantations for the production of large amounts of wood it has to be borne in mind that such plantations are monocultures and that the area used for them takes up space that might be used to grow food crops.
The intensity of solar radiation in Germany is in all regions sufficient to make effective use of solar heating. A solar heat system hardly gives rise to any CO2 emissions at all in comparison with conventional water heating systems - only the solar pump needs electricity, the production of which gives rise to CO2.Large-scale solar thermal installations (for apartment blocks, hotels, care homes, hospitals etc.) can achieve rates of up to 70% of the annual energy expenditure for heating water. Integration into the heating system can lead to roughly 20-30% of the total annual heating requirement being met by solar heat. Corresponding quantities of fossil fuels and CO2 emissions are saved through the use of solar heating.Significant reductions in harmful substance emissions and the documentation of the ecological arrangement of the building are further advantages of a solar thermal system. [BINE basisEnergie 4]
Economically and ecologically optimal is the use of solar thermal systems in combination with energy-efficient heating technology, that is, with a modern condensing boiler, wood pellet heating or heat pump heating. The energetic depreciation of a solar thermal installation – the period of time it takes for the system to generate as much energy as was used in its manufacture - lies between two and four years. In other words: in the course of its service life a system generates 13 times more energy than was needed for its manufacture. In contrast, fossil-fuel-based heating systems need large amounts of primary energy (coal, natural gas, crude oil) to provide a certain amount of useful energy (heat, power), meaning that they never depreciate in energetic terms.
The environmental relevance of electric heat pumps depends in the first instance on the amount of electricity needed to operate them. The actual environmental pollution is caused by the production and provision of this electricity. Heat pumps have an environmental advantage if, with a high seasonal performance factor, they can make levels of ambient heat (e.g. from water, soil, air/waste air) available for use that are in excess of the fossil fuels (primary energy) required for their operation.
Depending on their COP, electrical heat pumps are slightly more favourable in respect of their climate-change relevance (emissions of greenhouse gases) and their use of non-renewable energy resources than natural gas condenser-boiler heating. In comparison with heating systems using renewable energy carriers and local heating systems, however, electrical heat pumps compare unfavourably. If “green electricity”, with real-life benefits to the environment, is used to power electrical heat pumps then a decisive positive shift in the environmental balance occurs.
Well-designed electric heat pump systems can, in the course of a year, with one input unit of energy tap three times as much ambient heat, thus achieving a seasonal performance factor of 4. In order for example to provide 100 kWh of thermal heat, an electrical heat pump in this case uses 75 kWh of renewable ambient heat and 25 kWh of electricity, for which approx. 66 kWh of non-renewable primary energy is required. The remaining proportion of renewable energy is therefore 34 kWh or 34%.
Gas motor-driven heat pumps have ecological advantages in comparison to electrical heat pumps. How these advantages will develop in the future will depend on the development of the electricity and gas mix. [IFEU, WI 2008]
Coolants containing (H)CFCs were for a long time a central problem in the ecological balance of heat pumps. These are now largely forbidden in Germany. The HFC coolant mixtures R404A, R407C and R410A are mainly used instead. This have an ozone depletion potential (ODP) of 0 but are nonetheless powerful greenhouse gases. An environmentally-friendly alternative is offered by the propane (R290) coolant which has both no ODP and a negligible greenhouse potential.
The EU Flower is awarded to products that are proven to have less environmental impact throughout their life cycle than other similar products.
The European Union ecolabel distinguishes electrically and gas driven pumps with a maximum heating capacity of 100 kW which can also be used to heat water and for refrigeration. EU Ecolabel assessment and verification requirements address environmental compatibility, technical performance, and life cycle. Specifically, the criteria considered are: heating and cooling efficiency, refrigerants, noise, absence of hazardous substances as per RoHS, installer training, documentation, availability of spare parts, and detailed information.
National institutions are in charge of awarding the EU ecolabel in Member countries. In Germany, it is the RAL gGmbH.
The Blue Angel is the oldest official ecolabel in use in Germany. The label proprietor is the Federal Ministry for Environment, Nature Conservation and Nuclear Safety. The ecolabel provides an incentive to develop products that are more ecological and health-compatible.
The RAL-UZ 73 ecolabel is awarded to energy-efficient tube collectors and flat-plate collectors. The criteria for award tested are: annual collector output, substances in heat transfer medium and collector insulation material.
The RAL-UZ 111/112 ecolabels assess energy-saving wood pellet stoves and boilers that are low-emissions and efficient in operation on site. Additional criteria are efficient energy use, auxiliary power demand, limit values for NOx and CO emissions, organic substances, and dust.
The RAL-UZ 118 ecolabel is awarded to heat pumps that use less primary energy for the generation of heat energy than what current standards require or of conventional heating technology. Additional criteria for award of the Blue Angel are: type of refrigerant used, limit values of NOx and CO emissions, requirements of standard energy efficiency ratio, auxiliary power demand, and seasonal performance factor.
The RAL-UZ 121 ecolabel assesses energy-efficient heat pumps that use an electric compressor. Criteria for award of the Blue Angel are: TEWI limits, Global Warming Potential of the refrigerant used, and coefficient of performance (COP).
The RAL-UZ 124 ecolabel is awarded to energy-efficient hot water storage tanks that prove low heat loss ratios and are thus particularly efficient in saving energy resources and well-suited for use in combination with solar collectors. Additional criteria for award of the Blue Angel are: recyclable design and take-back conditions.
Award criteria are developed by the Federal Environment Agency in concert with manufacturers, testing institutions, and other experts and members of consumer associations. The independent Environmental Label Jury reviews and determines award criteria. The award itself is granted by the RAL gGmbH on behalf of the Federal Environment Agency.
Before taking a decision on a heating system, individual heat demand and various alternatives must be determined and considered. Decisive factors are heat standard and building connection to the grid (gas, district heating), and size of property (e.g. relevant to use of geothermal energy).
The tender recommendations presented in tabular form are oriented towards the requirements of the Blue Angel ecolabel for tube collectors and flat-plate collectors (RAL-UZ 73), wood pellet boilers (RAL-UZ 112), electric heat pumps (RAL-UZ 121), and hot water storage tanks (RAL-UZ 124). The tender recommendations for energy-efficient heat pumps using absorption and adsorption technology or operating by use of combustion engine-driven compressors go beyond the requirements for the Blue Angel ecolabel (RAL-UZ 118).
The bidder declares that the individual requirements have been met and presents testing documentation. Details on testing methods are listed in the award criteria. If the bidder has a contract for the use of the Blue Angel label, then it is assumed that compliance has already been reviewed and verified by RAL. A complete list of all products and suppliers certified by the Blue Angel is here: www.blauer-engel.de.
250 pupils of the community primary school in Siepen are educated in a building more than 100 years old. In the course of remediation work the construction authorities in the city of Remscheid reviewed various heat system concepts and, in consideration of a total cost analysis, opted for a wood pellet system. The 70-KW pellet unit is coupled with a gas-operated boiler which covers heat demand during peak periods. The pellet boiler provides 70% of heat, the gas boiler 30%. The warehouse for some 22 tonnes of pellets is in two newly built areas on a hillside location. Consumption in 2008 to provide heating for the 2,900-m2 school was 32.5 tonnes of pellets and 8,437 m³ gas. Replacement of the boiler saved 57.7 tonnes of CO2 per year. [NRW 2009 Siepen]
In remediation of its building stock the Beamten-Wohnungs-Verein of Berlin (BWV) chose to install a combination of natural gas condensing boilers and solar thermal energy.
An exemplary model is the solar collector system in the block of flats built in 1953 on Didostrasse in Berlin-Mariendorf. After remediation in 2005 its 125 residential units are now equipped with a combination of gas condensing boilers and a solar energy system that replaced the dated oil central heating systems with a few individual gas-fired boilers to supply hot water. The collector surface for hot water generation is 118 m², and an auxiliary heating system was also installed. The solar energy system is integrated in the circulation and anti-legionella circuit. Tenants save on heating costs shortly after the first few bills, affirming the BWV in the use of solar energy for the benefit of tenants and the climate. Solar energy output is 53,000 kWh/a, which amounts a final energy savings of approx. 6% and CO2 reduction of 12.4 t/a. [BEA 2008]
Contact:
Beamten-Wohnungs-Verein zu Berlin
www.bwv-berlin.de
Contact person: Martin Engling, Technical Director
The gymnasium on Baerwaldstraße in Friedrichshain-Kreuzberg is the first public building in Germany that uses waste water as a heat source. Heating and hot water are produced with a electric heat pump (base load) and a gas boiler (peak load). A 33-metre stainless steel heat exchanger was installed in the base of the duct. Warm waste water flows through v-shaped gutters and returns some of its heat to cool water that flows through the double-walled gutters. This cools the waste water by about one degree Celsius and warms the water in the gutter correspondingly. A pump transports water from the heat exchangers to the gymnasium heating system. Temperatures ranging from 8 to 16 degrees Celsius are not nearly enough to heat the gymnasium or provide hot water for showers. Waste water heating systems always require use of a heat pump, which have a closed circuit that circulates a refrigerant. The refrigerant extracts heat from the water and is condensed in a compressor. Thus the refrigerant heats up to a maximum 65 degrees Celsius and warms the water in a boiler that supplies radiators and showers in the gymnasium. The waste water heat is sufficient on most days to accommodate athletes’ needs. When demand spikes on especially cold winter days, the gas heating switches on automatically. [BEA 2009]
Contact:
Volker Gustedt
Berliner Energieagentur GmbH
Tel.: 0 30 / 29 33 30 - 19
Fax. 0 30 / 29 33 30 - 97
Email: gustedt@berliner-e-agentur.de