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Helsinki Energy commissioned a unique underground coal storage facility at its Salmisaari power plant site in Helsinki in summer 2004. Ex cavated from the site's bedrock, it features fully automated operation. This project, and the company's work in promoting district cooling and combined heat and power, highlight Helsinki Ener gy's commitment to being an innovative utility.

Helsinki Energy's new, fully automated coal storage facility, excavated in the bedrock under the company's Salmisaari power plant site, utilises vertical silo technology, and is the first of its kind in the world. The facility consists of four vertical silos, each 65 metres high and 40 metr es in diamet er. Together, the silos can store up to 250,000 tonnes of coal, or nearly half of the plant's annual coal requirement.

The lowest section of the facility is some 120 metres below sea level. A total of 4.5 kilometres of tunnel and 600 metres of vertical shafts were excavated for the project, generating more than one million cubic metres of blasted rock.

Graph 17. Helsinki Energy's unique new underground coal storage facility.

Everybody wins

Everybody wins as a result of the Salmisaari project: the environment, people living close by, and local business.

Moving Salmisaari's coal storage underground like this means that coal will no longer be handled above ground, which is a very valuable benefit, as the site is close to the centre of Helsinki. The new facility also frees up prime building land, and will enable the construction of approximately 100,000 square metres of new office and business space. Building work is expected to begin in autumn 2005.

Keeping cool in Helsinki

Helsinki Energy, a major supplier of district heating in Finland, introduced district cooling (DC) for airconditioning and cooling in 1998. Today, it is used yearround, winter and summer.

During the summer, surplus CHP heat and seawater is used to generate DC, with the help of absorption chillers and compressors. In the late autumn, winter, and spring, production is based solely on the efficient utilisation of cold seawater, by pumping seawater into DC heat exchangers.

Helsinki Energy's first DC system was a pilot project designed to supply industrial and office users in the Pitäjänmäki area of city, with 1.2 MW of DC, using a series of absorption chillers and accumulators. A 10 MW DC unit, featuring two absorption chillers, was commissioned at Salmisaari in 2001, serving offices and business buildings in the nearby district of Ruoholahti.

Additional cooling capacity of the same type will be added at Salmisaari underground, in space excavated as part of the new underground c oal storage facility. 7 MW of capacity was added in 2004, another 7 MW will be added in 2005, and 21 MW will come on stream in 2006.

Since the beginning of 2002, buildings in Sörnäinen have been supplied with DC using transportable cooling units; and the Kamppi area of central Helsinki was connected to the Salmisaari cooling plant in 2003.

The total connected cooling capacity of Helsinki Energy's DC network stood at 21 MW in 2004, and will reach some 35 MW by the end of 2005. By the end of 2010, the plan is to have over 100 MW of DC capacity.

A system for utilising the heat from treated wastewater as a source of both district heat and DC, with the help of heat pumps, is under construction. Due for completion in 2006, this will supply 90 MW of district heat and 60 MW of district cooling.

Key drivers

By increasing energy efficiency, DC reduces emissions of greenhouse gases, such as NOx and SO2, as well as particulates. Generation does not require the use of CFCs or HCFCs, can make use of surplus heat generated in the CHP process, seawater, or warm wastewater, and cuts noise levels by eliminating the need for compressor coolers inside buildings.

Used on a large scale, DC offers a much longer and more sustainable life cycle than separate, building-specific cooling systems. In addition, the use of DC cuts primary energy needs, as it reduces peak load levels by eliminating the power offtake required to generate cooling using local building equipment.

DC also offers added flexibility in terms of building design - as it gives increased space utilization, generates less noise than condensing fans and compressors, less condensation problems, and less risk of unwanted bacterial growth in cooling systems.

Environmentally friendly, reliable energy

Helsinki Energy is a major user of combined heat and power (CHP) solutions. These offer a number of environmental benefits, including greater overall efficiency, lower fuel use, and more controlled emissions

CHP use in Helsinki typically results in a fuel consumption efficiency rate exceeding 90%. By comparison, an equivalent quantity of fuel used solely for generating electricity would result in a maximum fuel consumption efficiency rate of 40-50%.

The switch-over from individually heated buildings to centrally generated district heat began in the 1950s, and district heat now covers over 90% of the city's infrastructure. Air quality has steadily improved as a result. Filtered emissions now issue from a small number of high stacks in dispersed locations; low individual chimneys have almost vanished from the urban landscape.

Helsinki Energy is one of the world's leading CHP specialists, and Finland one of the leading countries in the field. Helsinki's CHP-based district heating system was awarded the United Nations Environmental Prize in 1990 - and Helsinki Energy's CHP and district heating expertise has been used by utilities and generators in countries as varied as Korea, China, Japan, Canada, Britain, and Russia.

> Marko V. J. Riipinen
(Published in High Technology Finland )