Renewable heat is a renewable energy application and refers to renewable heat, rather than electrical power (eg replacing fossil fuel boilers using solar thermal concentration to feed the radiator). Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers to recover lost heat. Significant attention is also applied to isolation.
Many cooler countries consume more energy for heating than electric power. For example, in 2005 the United Kingdom consumed 354 TWh of electric power, but had a heat requirement of 907 TW, most (81%) was filled with gas. The housing sector alone consumes 550 TWD of energy for heating, especially in the form of gas. Almost half of the final energy consumed in the UK (49%) is in the form of heat, of which 70% is used by households and in commercial and public buildings. Households use heat mainly for heating the room (69%) and heating water.
The relative competitiveness of renewable electricity and renewable heat depends on a national approach to energy and environmental policies. Some renewable technologies (whether for heat, electricity or transport) are competitive with fossil fuels without some form of grading or carbon subsidies. In these countries, such as Sweden, Denmark and Finland, where government intervention is closest to a carbon neutral form (carbon and energy tax), renewable heat has played a major role in enormous renewable contributions to the end of energy consumption. In these countries, such as Germany, Spain, the US and the UK, where government intervention has been set at different levels for different technologies, uses and scales, the contribution of renewable energy and renewable electricity technologies depends on the relative level of support, and has resulted in general in lower renewable contributions to final energy consumption.
Video Renewable heat
The leading renewable thermal technology
Solar heating
Solar heating is a style of building construction that uses the energy of summer or winter sunlight to provide an economic supply of primary or extra heat to the structure. Heat can be used for space heating (see solar heat) and water heater (see solar hot water). The solar heater design is divided into two groups:
- Passive solar heating depends on the design and structure of the house to collect heat. The design of passive solar buildings should also consider the storage and distribution of heat, which can be done passively, or use the airways to actively draw heat into the building's foundation for storage. One such design measured raised the home temperature to 24 ° C (75 ° F) on a partially sunny winter day (-7 ° C or 19 ° F), and it is claimed that this system provides passively for the most part heating the building. A 4,000-square-foot house (370 m 2 ) costs $ 125 per square foot (or 370 m 2 for $ 1,351/m 2 ), similar to traditional new home costs.
- Active solar heating uses a pump to move air or liquid from a solar collector into a building or storage area. Applications such as solar air heaters and solar water heaters typically capture solar heat in panels that can then be used for applications such as space heating and residential water heater supplementation. Unlike the photovoltaic panels, which are used to generate electricity, solar heating panels are cheaper and capture a much higher proportion of solar energy.
Solar heating systems typically require a small additional backup heating system, either conventional or renewable.
Geothermal heating
Geothermal energy is accessed by drilling water or steam wells in a process similar to drilling for oil. Geothermal energy is a great source of energy and heat that is very large and poorly utilized clean (emitting little or no greenhouse gases), reliable (95% system availability), and homegrown (making the population less dependent on oil).
The Earth absorbs solar energy and stores it as heat in the oceans and underground. The soil temperature remains constant at a point 42 to 100 Â ° F (6 to 38 Â ° C) throughout the year depending on where you live on earth. The geothermal heating system utilizes the consistent temperature found beneath the Earth's surface and uses it to heat and cool buildings. This system consists of a series of pipes installed underground, connected to a pipe in the building. A pump circulates the liquid through the circuit. In winter, the fluids in the pipes absorb the geothermal heat and use them to heat buildings. In summer the liquid absorbs heat from the building and throws it on earth.
Heat pump
Heat pumps work to move heat from one place to another, and can be used for heating and air conditioning. Despite being capital intensive, heat pumps are economical to run and can be powered by renewable electricity. Two common types of heat pumps are air-borne heat pumps (ASHP) and direct-sourced (GSHP) heat pumps, depending on whether heat is transferred from the air or from the ground. The air source heat pump is ineffective when the outside air temperature is lower than -15 Â ° C, while the heat source heat pump is not affected. The efficiency of a heat pump is measured by a performance coefficient (CoP): For each electric unit used for heat pumping, the air source heat pump produces 2.5 to 3 units of heat (ie has CoP 2.5 to 3), while GSHP produces 3 to 3 , 5 units of heat. Based on current fuel prices for the United Kingdom, assuming CoP 3-4, GSHP is sometimes a cheaper form of space heating than electricity, oil, and solid fuel heating. The heat pump can be connected to intakeasonal heat storage (hot or cold), doubling CoP from 4 to 8 by extracting heat from warmer soil.
Inter-star heat transfer
A heat pump with Interseasonal Heat Transfer incorporates active solar collection to store summer excess heat in thermal banks with ground-source heat pumps to extract it for heating the room in winter. This reduces the required "Lift" and doubles CoP from the heat pump because the pump starts with the warmth of the thermal bank instead of the cold from the ground.
CoP and lift
CoP heat pump increases due to temperature difference, or "Lift", decreases between heat source and destination. CoP can be maximized at design time by selecting a heating system that requires only low end water temperatures (eg under floor heating), and by selecting a heat source with a high average temperature (eg, soil). Domestic hot water (DHW) and conventional radiators require high water temperatures, affecting the choice of heat pump technology. Low temperature radiators provide an alternative to conventional radiators.
Resistive electric heating
Renewable electricity can be generated by hydro power, solar, wind, geothermal and by burning biomass. In some countries where renewable electricity is not expensive, heating resistance is common. In countries like Denmark where electricity is expensive, it is not permissible to install electric heaters as a major heat source. Wind turbines have more output at night when there is a small electricity demand, storage heater consumes electricity at lower costs at night and releases heat during the day.
Heating wood pellets
Wood-pellet heating and other types of wood heating systems have achieved their greatest success in heating places that are outside the gas network, usually those previously heated using heating oil or coal. Solid wood fuel requires a large amount of dedicated storage space, and special heating systems can be expensive (although grant schemes are available in many European countries to offset these capital costs.) Low fuel costs mean that wood fuel heating in Europe is often able to reach periods refund less than 3 to 5 years. Due to large fuel needs, wood fuel can be less attractive in the urban housing scenario, or for locations connected to the gas network (although gas price increases and supply uncertainty mean that wood fuel becomes more competitive.) There are also increasing concerns increased. on air pollution from wood heating versus oil or hot gas, especially fine particulates.
Wood-stove heating
Burning wood fuel in open flame is very inefficient (0-20%) and pollution due to low temperature partial combustion. In the same way that windy buildings lose heat through the loss of warm air through poor sealing, open flames are responsible for large heat losses by attracting very much the volume of warm air out of the building.
The design of modern wood stoves allows more efficient combustion and then heat extraction. In the United States, the new wood stove is certified by the US Environmental Protection Agency (EPA) and burns cleaner and more efficiently (overall efficiency is 60-80%) and takes the warmer air volume smaller than the building.
"Cleaner" should not, however, be confused with the net. An Australian study of real-life emissions from woodheaters meeting current Australian standards, found that average particle emissions burned 9.4 g/kg of wood (range 2.6 to 21.7). A heater with an average wood consumption of 4 tons per year therefore emits 37.6 kg of PM2.5, ie particles less than 2.5 micrometers. This can be compared to passenger cars that meet the current Euro 5 standard (introduced September 2009) of 0.005 g/km. So one new wood heater emits as much as PM2.5 per year as 367 passenger cars each driving 20,000 km per year. A recent European study identified PM2.5 as the most dangerous air pollutant for health, causing approximately 492,000 premature deaths. The next worst pollutant, ozone, is responsible for 21,000 premature deaths.
Due to problems with pollution, the Australian Lung Foundation recommends using alternative ways of climate control. American Lung Association "strongly recommend the use of a cleaner and less toxic source of heat.Change fireplaces or wood burning stoves to use natural gas or propane will eliminate exposure to harmful toxins produced by wood burning including dioxins, arsenic and formaldehyde.
"Renewable" should not be equated with a "neutral greenhouse". A recent paper reviewed by colleagues found that, even if burning firewood from sustainable supplies, methane emissions from typical Australian heater that meet current standards lead to more global warming than warming the same house with gas. However, since most firewood sold in Australia does not come from sustainable supplies, Australian households that use wood heating often cause more global warming than heating the same three homes as gas.
High efficiency stoves must meet the following design criteria:
- Well sealed and precisely calibrated to produce low but sufficient air volume. Air flow limitation is very important; Lower cold air flow cools the furnace less (higher temperatures are reached). It also allows a longer time to extract heat from the flue gas, and draw less heat from the building.
- The furnace should be well insulated to increase the combustion temperature, and thus its fittings.
- A well-insulated furnace emits a bit of heat. So heat must be extracted not from the exhaust channel. The heat absorption efficiency is higher when the heat exchange channel is longer, and when the flue gas flow is slower.
- In many designs, heat exchange channels are constructed from rock or rock masses that are heavily absorbing heat. This design causes the absorbed heat to emit in a longer period - usually a day.
Natural gas that can be updated
Renewable natural gas is defined as gases obtained from improved biomass to qualities similar to natural gas. By improving the quality of natural gas, it becomes possible to distribute gas to customers through existing gas networks. According to the Dutch Energy Research Center, renewable natural gas is 'cheaper than alternatives where biomass is used in combined heat and power plants or local firms'. Energy unit costs are decreased through 'profitable scale and hours of operation', and the cost of end user capital is eliminated through distribution through existing gas networks.
Maps Renewable heat
Energy efficiency
The renewable heat goes hand in hand with energy efficiency. Indeed, the renewable heating project relies heavily on its success in energy efficiency; in the case of solar heating to cut dependence on additional heating needs, in the case of wood fuel heating to cut the cost of purchasing wood and stored volumes, and in the case of heat pumps to reduce the size and investment in heat pumps, heat sinks and electricity costs.
Two major types of improvements can be made to building energy efficiency:
Isolation
Insulation repair can reduce energy consumption, making the room less expensive for heat and cold. However, existing housing is often difficult or expensive to repair. Newer buildings can benefit from many superinsulation techniques. Older buildings can benefit from some types of improvements:
- Solid wall insulation : Buildings with solid walls can take advantage of internal or external insulation. The external wall insulation involves adding a weatherproof insulation panel or other treatment to the outside of the wall. Alternatively, internal wall insulation can be applied by insulating/laminating a finished plaster board, or other method. The thickness of internal or external insulation usually ranges between 50 and 100 mm.
- Insulating wall cavity : A building with a cavity wall can utilize insulation that is pumped into the cavity. This form of insulation is very cost effective.
- Programmable thermostats allow room heating and cooling to be switched off depending on time, day of the week, and temperature. A bedroom, for example, does not need to be heated during the day, but the living room does not need to be heated at night.
- Insulating roof
- Insulated windows and doors
- Draft printing
Under-floor heating
Under-floor heating is sometimes more energy efficient than traditional heating methods:
- Water circulates in the system at low temperatures (35 ° C - 50 ° C) makes gas boilers, wood-fired boilers, and heat pumps significantly more efficient.
- Heated under-floor heating rooms near the ceiling, where heat is not needed, but a warmer soil surface, where comfort is most needed.
- Traditional radiators are often positioned under poorly insulated windows, heating them unnecessarily.
Wastewater heat recovery
It is possible to recover large amounts of heat from waste hot water through hot water recycling. Large consumption of hot water is a sink, shower, bathtub, dishwasher, and laundry. An average of 30% of the domestic hot water property is used for bathing. Incoming fresh water usually has a temperature much lower than the waste water from the shower. The cheaper heat exchangers recover an average of 40% of the normally wasted heat, by heating cold water in with the heat from the waste water out.
See also
References
External links
- Heat pumps based on R744 (CO 2 ) FAQ
- Heat pumping the Waiting Path of Global Warming - Information from Heat Pump & amp; Japan Thermal Storage Technology Center
- Department of Trade and Industry, 2005 study on Renewable Heat
- The Renewable Heat incorporates asphalt solar collector, thermal bank and ground source heat pump.
- Energy Saving Information on House Insulation
- Gill's report on biomass in the UK - download
- Solid wall insulation
- Insulation wall cavity
Source of the article : Wikipedia
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