District Energy - 2008 4th Quarter

South Korea Taps
Solar Energy

South Korea has a developed a solar district heating system, completed last year at the Korea District Heating Corp. (KDHC) plant at Seongnam, near Seoul. The solar heating system can supply hot water at about 90 degrees C (194 F) for district heating. The 1,060-sq-m ( 11,410-sq-ft) facility uses both flat and vacuum-type solar panels and supplies the heat directly without the need for a heat storage tank.

A joint investment of KDHC and Korea’s Ministry of Commerce, Industry and Energy, the project cost 1. 6 billion won ($1.4 million) in research and development and another 700 million won ($604,900) to construct the facility. The system can produce 500- 600 Gcal of heat annually, equivalent to 50-60 tons of crude oil, and is expected to reduce carbon dioxide emissions by about 120 tons. The new system provides a facility for further study of the use of solar energy in district heating by the Korea Institute for Energy Research.

Sources: Korea Energy Policy Brief and Korea Herald.

fueled boiler plant. The plant yields close to 4 GWh/year out of a total load of about 100 GWh/year, so 4 percent of the total load requirement is met via solar, whereas the wood chip plant provides 96 percent. Note that the 4 percent solar heat in Kungälv district heating system is equivalent to solar heat from 2,000 individual solar domestic hot water systems, i.e., approximately the same number of systems installed in Sweden in a one-year period.

The Danish large-scale solar heating plants are used in small district heating systems, and all collectors are ground-mounted. Based on Swedish experiences, the first Danish plant was built in Saltum in 1987, still in operation with 1,000 sq m ( 10,764 sq ft) of ground-mounted collectors.

In 1995, Danish district heating supplier Marstal Fjernvarme A.m.b.a. decided to establish about 8,000 sq m (86,111 sq ft) of solar collectors and a 2,000-cu-m (528,344-gal) water storage tank to cover up to 15 percent of its heating load. As noted in table 1, the Marstal plant is now expanded to 18,300 sq m (196,980) and 12. 8 MWth and is so far the largest solar heating plant in Europe. A recent study of the future

potential for solar district heating in Denmark led to the construction of two new plants in the past two years.

Block Heating

In addition to being used in district heating, solar energy is also used in ‘block heating’ in Europe. Block heating systems are boiler plants that serve a smaller number of buildings than district systems do. These are often, but not necessarily, residential in nature: campuses, for example, could also be served by block heating. (The distinction between district and block heating is reflected in the Swedish language, for example, as fjärrvärme and närvärme, respectively, and in German as Fernwärme and Nahwärme).

The Swedish housing company EKSTA Bostads AB pioneered the use of roof-integrated solar collectors to serve new residential areas already in the 1980s. At present EKSTA owns and operates about 7,000 sq m (75,347 sq ft) of roof-integrated collectors. Initially EKSTA used site-built collectors, but since 1995 has used a roof module collector – mounted directly on the roof trusses – on a couple of new and existing buildings. This development has resulted in even better integration in the building process, as well as further reduced investment cost and improved thermal performance.

A recent study of the future
potential for solar district
heating in Denmark led to
the construction of two new
plants in the past two years.

The German large-scale solar heating plants are mainly applied in new residential building areas using roof-integrated or mounted collectors. Some of the large projects have so-called ‘solar roofs.’ Until 2003, eight projects with seasonal storage, and about 50 large- to medium-scale projects with short-term storage, had been realized within the Solarthermie2000 program (a 10-year initiative of the German Federal Ministry for Economics and Technology to fund large-scale solar-assisted heating plants).

There are two German plants that each have more than 5,000 sq m ( 53,820 sq ft) of roof-integrated collectors in Neckarsulm and Crailsheim, and a new plant with 2,900 sq m ( 31,215 sq ft) is under construction in Munich.

In Austria, the first large-scale solar plant – a small local biomass-fired block heating plant complemented with a solar system – was built in Deutsch-Tschantschendorf in 1995. Graz is now the large-scale solar city of Austria with the first plant built in 2002 and two new plants – the largest one with more than 5,000 sq m ( 53,820 sq ft) of collectors connected to the district heating network.

In the Netherlands, the most widely implemented application of large solar heating systems is block heating serving collective housing, institutions and homes for the elderly. Most systems have about 100 sq m ( 1,076 sq ft) of solar collectors. Some systems are larger, however, such as the Brandaris building in Amsterdam with 700 sq m ( 7,535 sq ft) of rooftop-mounted collectors. Two large-scale plants are designed with seasonal storage: a recently built plant with 2,900 sq m ( 31,215 sq ft) of solar collectors connected to an aquifer storage in Schalkwijk.

Other Applications

Several of the large solar systems in the Netherlands and Greece are industrial heat applications. The Perfetti Van Melle (a confectionary and gum maker) factory in Breda, the Netherlands, has 2,400 sq m ( 25,833 sq ft) of flat-plate collectors. The first large-scale solar cooling plant in Greece – with 2,700 sq m ( 29,063 sq ft) of flat-plate collectors providing heat to two 350-k W adsorption chillers – was installed in Athens in 1998. At present, there are also a couple of recent large-scale solar cooling plants in Italy and Spain, e.g., a plant with 1,500 sq m ( 16,146 sq ft) of solar collectors for industry cooling by Inditex in Spain. The majority of solar cooling plants are equipped with absorption machines (lithium bromide), but the largest one is equipped with two adsorption machines.