Central solar heating is the provision of central heating and hot water from solar energy by a system in which the water is heated centrally by arrays of solar thermal collectors (central solar heating plants - CSHPs) and distributed through district heating pipe networks (or 'block heating' systems in the case of smaller installations).
For block systems, the solar collectors are typically mounted on the building roof tops. For district heating systems the collectors may instead be installed on the ground.
Central solar heating can involve large-scale thermal storage, scaling from diurnal storage to seasonal thermal energy storage (STES). Thermal storage increase the solar fraction - the ratio between solar energy gain to the total energy demand in the system - for solar thermal systems. Ideally, the aim for applying seasonal storage is to store solar energy collected in the summer time to the winter month.
Compared to small solar heating systems (solar combisystems), central solar heating systems have better price-performance ratios due to the lower installation price, the higher thermal efficiency and less maintenance. In some countries such as Denmark large-scale solar district heating plants are financially fully competitive to other forms of heat generation. [1]
Central solar systems can also be used for solar cooling in the form of district cooling. In this case, the overall efficiency is high due to the high correlation between the energy demand and the solar radiation.
Name | Country | Owner | Solar collector size | Thermal Power | Annual production | Installation year | Storage volume | Storage type Facilities | Collector manufacturer |
---|---|---|---|---|---|---|---|---|---|
m2 | MWth | GWh | m3 | ||||||
Silkeborg | DK | Silkeborg Fjernvarme | 157,000 | 110 | 80 | 2016 | 64,000 | Water tank | ARCON (DK) [2] [3] [4] [5] [6] |
Vojens | DK | Vojens Fjernvarme | 70,000 | 50 | 35 | 2012-2015 | 203,000 | Insulated water pond Water tank | ARCON (DK) [7] [8] [9] |
Port Augusta, South Australia | Australia | Sundrop Farms | 51,500 | 36.4 | 2016 | Aalborg CSP. Desalination for vegetables. 1.5 MW electricity [10] [11] | |||
Gramm | DK | Gram Fjernvarme | 44,801 | 31 | 20.8 | 2009- | 122,000 | Insulated water pond. 10MW electric boiler 900 kW heat pump | [12] [13] |
Gabriela Mistral, El Loa, Atacama Desert | Chile | CODELCO mine | 43,920 | 27-34 | 52-80 | 2013 | 4,300 | Water tank | ARCON (DK). Supplies an electrowinning copper process [5] [14] [15] [16] |
Dronninglund | DK | 37,573 | 26 | 18 | 2014 | 60,000 | Insulated water pond | ArCon (DK) [17] [18] | |
Zhongba, 4,700 metres altitude [19] | Tibet (China) | 34,650 | 20 | 2019 | 15,000 | Water tank | ArCon [20] [21] | ||
Marstal | DK | Marstal Fjernvarme | 33,300 | 24 | 13.4 | 1996–2002, 2020 | 2,100 3,500 70,000 | Water tank Sand/water ground pit Insulated water pond with new lid | Sunmark / ARCON (DK). Feeds 0.75 MW ORC turbine [22] [23] [24] [25] [26] |
Ringkøbing | DK | 30,000 | 22.6 | 14 | 2010-2014 | ArCon [27] | |||
Brønderslev | DK | 27,000 | 16.6 | 8,000 | Water tank | CSP parabolic trough [28] [29] [30] | |||
Langkazi, 4,600 metres altitude [31] | Tibet (China) | 22,000 | 2018 | 15,000 | Insulated water pond | ArCon [20] [32] | |||
Hjallerup | DK | 21,432 | [33] | ||||||
Vildbjerg | DK | 21,234 | 14.5 | 9.5 | 2014 | ArCon [34] | |||
Helsinge | DK | Helsinge Fjernvarme | 19,588 | 14 | 9.4 | 2012-2014 | [35] | ||
Hadsund | DK | Hadsund Fjernvarme | 20,513 | 14 | 11.5 | 2015 | ARCON (DK) [36] | ||
Nykøbing Sjælland | DK | 20,084 | 14 | 9.5 | ARCON (DK) [37] | ||||
Gråsten | DK | 19,024 | 13 | 9.7 | 2012 | ARCON (DK) [38] | |||
Brædstrup | DK | Brædstrup Fjernvarme | 18,612 | 14 | 8.9 | 2007/2012 | 5,000 19,000 | Water tank Borehole storage, insulated by seashells | ARCON (DK) [39] [40] |
Tarm | DK | 18,585 | 13.1 | 9 | 2013 | ARCON (DK) [41] | |||
Jetsmark | DK | 15,183 | 10.6 | 7.6 | 2015 | Arcon/Sunmark (DK) [42] | |||
Oksbøl | DK | 14,745 | 9.9 | 7.7 | 2010/2013 | Sunmark (DK) [43] | |||
Jægerspris | DK | 13,405 | 8.6 | 6 | 2010 | Sunmark (DK) [44] | |||
SydLangeland | DK | 12,500 | 7.5 | 7.5 | 2013 | Sunmark (DK) [45] | |||
Grenaa | DK | 12,096 | 8.4 | 5.8 | 2014 | Arcon (DK) [46] | |||
SydFalster | DK | 12,094 | 8.5 | 6 | 2011 | Arcon (DK) [47] | |||
Hvidebæk | DK | 12,038 | 8.6 | 5.7 | 2013 | Arcon (DK) [48] | |||
Sæby | DK | Sæby Fjernvarme | 11,866 | 8 | 6.3 | 2011 | Sunmark (DK) [49] | ||
Toftlund | DK | 11,000 | 7.4 | 5.4 | 2013 | Sunmark (DK) [50] | |||
Kungälv | SE | Kungälv Energi AB | 10,048 | 7.0 | 4.5 | 2000 | 1,000 | Water tank | ARCON (DK) |
Svebølle-Viskinge | 10,000 | 5.3 | 5 | 2011/2014 | [51] | ||||
Karup | DK | 8,063 | 5.4 | 3.7 | 2013 | ARCON (DK) [52] | |||
Strandby | DK | Strandby Varmeværk | 8,000 | 5.6 | 3.6 | 2007 | ARCON (DK) [53] | ||
Nykvärn | SE | Telge Energi AB | 7,500 | 5.3 | 3.4 | 1985 | 1,500 | Water tank | Teknoterm (SE) ARCON (DK) |
Crailsheim | DE | 7,300 | 2012 | 37,500 | Borehole | Wagner, Schüco, Aquasol, Asgard [54] [55] | |||
Ærøskøbing | DK | Ærøskøping Fjernvarme | 7,050 | 3.4 | 3 | 1998/2010 | 1,200 | Water tank | ARCON/Sunmark (DK) [56] |
La Parreña mine | Mexico | Peñoles | 6,270 | 4,4 | 660 | Water tank | ARCON (DK). Supplies an electrowinning process [57] | ||
Falkenberg | SE | Falkenberg Energi AB | 5,500 | 3.9 | 2.5 | 1989 | 1,100 | Water tank | Teknoterm (SE) ARCON (DK) |
Graz | AT | Energie Graz | 6,000 | 2018 | Water tank | ||||
Neckarsulm | DE | Stadtwerke Neckarsulm | 5,044 | 3.5 | 2.3 | 1997 | 25,000 | Soil duct heat exchanger | Sonnenkraft (DE) ARCON (DK) |
Ulsted | DK | Ulsted Fjernvarme | 5,000 | 3.5 | 2.2 | 2006 | 1,000 | Water tank | ARCON (DK) |
Friederichshafen | DE | Technische Werke Fried. | 4,250 | 3.0 | 1.9 | 1996 | 12,000 | Concrete tank in ground | ARCON (DK) |
Source: Jan Erik Nielsen, PlanEnergi, DK.
Hereafter you find a plant in Rise (DK) with a new collector producer, Marstal VVS (DK), a plant in Ry (DK), one of the oldest in Europe, a plant in Hamburg and a number of plants below 3,000 m2. It may be relevant mentioning, that the island of Ærø in Denmark has three of the major CSHP, Marstal, Ærøskøping and Rise.
![]() | The examples and perspective in this article may not represent a worldwide view of the subject.(May 2010) |
Sweden has played a major role in the development of large-scale solar heating. According to (Dalenbäck, J-O., 1993), the first steps were taken in the early seventies in Linköping, Sweden, followed by a mature revision in 1983 in Lyckebo, Sweden. Inspired by this work, Finland developed its first plant in Kerava, and the Netherlands built a first plant in Groningen. These plants are reported under the International Energy Agency by (Dalenbäck, J-O., 1990). Note that these plants did already combine CSHPs with large-scale thermal storage.
The first large-scale solar collector fields were made on-site in Torvalle, Sweden, 1982, 2000 m2 and Malung, Sweden, 640 m2. Prefabricated collector arrays were introduced in Nykvarn, Sweden, 4000 m2 in 1985. There was from the beginning a strong international perspective and cooperation within this research field, through investigation with the European Communities (Dalenbäck, J-O., 1995) and the International Energy Agency (Dalenbäck, J-O., 1990). Denmark did enter this research area parallel to the Swedish activities with a plant in Vester Nebel in 1987, one plant in Saltum in 1988 and one in Ry in 1989, taking over the know-how for prefabricated solar collectors of large size by the Swedish company Teknoterm by the dominating company ARCON, Denmark. In the later 1990s Germany and Switzerland were active among others with plants in Stuttgart and Chemnitz.
Due to cheap land prices, in the Nordic countries new collector arrays are ground-mounted (concrete foundations or pile-driven steel) in suitable areas (low-yield agricultural, industry etc.). Countries with high ground prices tend to place solar collectors on building roofs, following the 'block plant' variant of CSHPs. In Northern Europe, 20% solar heat of annual heating requirement is the economic optimum in a district heating plant when using above-ground storage tanks. If pond storage is used, the solar contribution can reach 50%. [58]
By 1999 40 CSHPs were in operation in Europe generating about 30 MW of thermal power [ permanent dead link ].
Central solar heating is a sub-class of 'large-scale solar heating' systems - a term applied to systems with solar collector areas greater than 500 m2.
Aquifers, boreholes and artificial ponds (costing €30/m3) are used as heat storage (up to 90% efficient) in some central solar heating plants, which later extract the heat (similar to ground storage) via a large heat pump to supply district heating. [59] [60] Some of these are listed in the table above.
In Alberta, Canada the Drake Landing Solar Community has achieved a world record 97% annual solar fraction for heating needs, using solar-thermal panels on the garage roofs and thermal storage in a borehole cluster. [61] [62] [63]
Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.
Solar energy is radiant light and heat from the Sun that is harnessed using a range of technologies such as solar power to generate electricity, solar thermal energy, and solar architecture. It is an essential source of renewable energy, and its technologies are broadly characterized as either passive solar or active solar depending on how they capture and distribute solar energy or convert it into solar power. Active solar techniques include the use of photovoltaic systems, concentrated solar power, and solar water heating to harness the energy. Passive solar techniques include orienting a building to the Sun, selecting materials with favorable thermal mass or light-dispersing properties, and designing spaces that naturally circulate air.
Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy for use in industry, and in the residential and commercial sectors. Solar thermal collectors are classified by the United States Energy Information Administration as low-, medium-, or high-temperature collectors. Low-temperature collectors are generally unglazed and used to heat swimming pools or to heat ventilation air. Medium-temperature collectors are also usually flat plates but are used for heating water or air for residential and commercial use.
Solar water heating (SWH) is heating water by sunlight, using a solar thermal collector. A variety of configurations are available at varying cost to provide solutions in different climates and latitudes. SWHs are widely used for residential and some industrial applications.
A parabolic trough collector (PTC) is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The sunlight which enters the mirror parallel to its plane of symmetry is focused along the focal line, where objects are positioned that are intended to be heated. In a solar cooker, for example, food is placed at the focal line of a trough, which is cooked when the trough is aimed so the Sun is in its plane of symmetry.
District heating is a system for distributing heat generated in a centralized location through a system of insulated pipes for residential and commercial heating requirements such as space heating and water heating. The heat is often obtained from a cogeneration plant burning fossil fuels or biomass, but heat-only boiler stations, geothermal heating, heat pumps and central solar heating are also used, as well as heat waste from factories and nuclear power electricity generation. District heating plants can provide higher efficiencies and better pollution control than localized boilers. According to some research, district heating with combined heat and power (CHPDH) is the cheapest method of cutting carbon emissions, and has one of the lowest carbon footprints of all fossil generation plants.
Micro combined heat and power, micro-CHP, μCHP or mCHP is an extension of the idea of cogeneration to the single/multi family home or small office building in the range of up to 50 kW. Usual technologies for the production of heat and power in one common process are e.g. internal combustion engines, micro gas turbines, stirling engines or fuel cells.
Thermal energy storage (TES) is the storage of thermal energy for later reuse. Employing widely different technologies, it allows surplus thermal energy to be stored for hours, days, or months. Scale both of storage and use vary from small to large – from individual processes to district, town, or region. Usage examples are the balancing of energy demand between daytime and nighttime, storing summer heat for winter heating, or winter cold for summer cooling. Storage media include water or ice-slush tanks, masses of native earth or bedrock accessed with heat exchangers by means of boreholes, deep aquifers contained between impermeable strata; shallow, lined pits filled with gravel and water and insulated at the top, as well as eutectic solutions and phase-change materials.
Renewable heat is an application of renewable energy referring to the generation of heat from renewable sources; for example, feeding radiators with water warmed by focused solar radiation rather than by a fossil fuel boiler. Renewable heat technologies include renewable biofuels, solar heating, geothermal heating, heat pumps and heat exchangers. Insulation is almost always an important factor in how renewable heating is implemented.
Waste heat is heat that is produced by a machine, or other process that uses energy, as a byproduct of doing work. All such processes give off some waste heat as a fundamental result of the laws of thermodynamics. Waste heat has lower utility than the original energy source. Sources of waste heat include all manner of human activities, natural systems, and all organisms, for example, incandescent light bulbs get hot, a refrigerator warms the room air, a building gets hot during peak hours, an internal combustion engine generates high-temperature exhaust gases, and electronic components get warm when in operation.
Seasonal thermal energy storage (STES), also known as inter-seasonal thermal energy storage, is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever needed, such as in the opposing season. For example, heat from solar collectors or waste heat from air conditioning equipment can be gathered in hot months for space heating use when needed, including during winter months. Waste heat from industrial process can similarly be stored and be used much later or the natural cold of winter air can be stored for summertime air conditioning.
Denmark has considerable sources of oil and natural gas in the North Sea and ranked as number 32 in the world among net exporters of crude oil in 2008. Denmark expects to be self-sufficient with oil until 2050. However, gas resources are expected to decline, and production may decline below consumption in 2020, making imports necessary. Denmark imports around 12% of its energy.
The Drake Landing Solar Community (DLSC) is a planned community in Okotoks, Alberta, Canada, equipped with a central solar heating system and other energy efficient technologies. This heating system is the first of its kind in North America, although much larger systems have been built in northern Europe. The 52 homes in the community are heated with a solar district heating system that is charged with heat originating from solar collectors on the garage roofs and is enabled for year-round heating by underground seasonal thermal energy storage (STES).
Energy recycling is the energy recovery process of using energy that would normally be wasted, usually by converting it into electricity or thermal energy. Undertaken at manufacturing facilities, power plants, and large institutions such as hospitals and universities, it significantly increases efficiency, thereby reducing energy costs and greenhouse gas pollution simultaneously. The process is noted for its potential to mitigate global warming profitably. This work is usually done in the form of combined heat and power or waste heat recovery.
Concentrated solar power systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight into a receiver. Electricity is generated when the concentrated light is converted to heat, which drives a heat engine connected to an electrical power generator or powers a thermochemical reaction.
A hot water storage tank is a water tank used for storing hot water for space heating or domestic use.
The International Energy Agency Solar Heating and Cooling Technology Collaboration Programme (IEA SHC TCP) is one of over 40 multilateral Technology Collaboration Programmes (also known as TCPs) of the International Energy Agency. It was one of the first of such programmes, founded in 1977. Its current mission is to "advance international collaborative efforts for solar energy to reach the goal set in the vision of contributing 50% of the low temperature heating and cooling demand by 2030.". Its international solar collector statistics Solar Heat Worldwide serves as a reference document for governments, financial institutions, consulting firms and non-profit/non-governmental organizations.
Solar power in Denmark amounts to 3,645 MW of grid-connected PV capacity at the end of March 2024, and contributes to a goal to use 100% renewable electricity by 2030 and 100% renewable energy by 2050. Solar power produced 9.3% of Danish electricity generation in 2023, the highest share in the Nordic countries.
Renewable energy sources such as solar, wind, tidal, hydro, biomass, and geothermal have become significant sectors of the energy market. The rapid growth of these sources in the 21st century has been prompted by increasing costs of fossil fuels as well as their environmental impact issues that significantly lowered their use.
Denmark is a leading country in renewable energy production and usage. Renewable energy sources collectively produced 81% of Denmark's electricity generation in 2022, and are expected to provide 100% of national electric power production from 2030. Including energy use in the heating/cooling and transport sectors, Denmark is expected to reach 100% renewable energy in 2050, up from the 34% recorded in 2021.
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