At the inauguration event on 23rd of September, the utility ‘Stadtwerke Senftenberg’ as operator and Ritter XL Solar GmbH as manufacturer and planner of the collector field could already look back on more than four weeks of successful operation. Thanks to the late summer weather, the plant could already deliver more than 20% of its predicted yearly yield, said Detlef Moschke, director of the utility. ‘Already during the weekend from 26th to 28th of August, we measured 85,6 MWh supplied. It is enough to cover the basic load of 3 000 households in Senftenberg’, said Moschke.By such summerly conditions, the solar plant is the only heat supplier feeding in the net. Via the newly built heat exchanger, the heat is normally fed directly into the feed-in pipe of the district heating system. The CPC evacuated tube collectors deliver temperatures from 85 to 110°C. In case of bad irradiation conditions at the beginning and end of days or in case of cloudy sky, the plant can also feed in the return pipe of the district heating network, where lower temperatures and pressures have to be overcome.

The collector field of Senftenberg, unlike some other smaller solar projects from Ritter XL, is hydraulically separated from the district heating net. Even if the collectors are operated with water without any antifreeze fluid, two heat exchangers separate them from the district heating net. Rolf Meißner, director of Ritter XL explains that the hydraulic separation is simply a precaution due to the insufficient water quality in the district heating of Senftenberg.

The area of 2,2 hectares where the plant is built is located on a previous waste disposal site from the City of Senftenberg, where the recultivation process ended last year. It was a chance for Senftenberg that a strand of the district heating net is passing directly along the site. Like this, a short transmission pipe of a few hundred meters is enough to connect the solar plant with the district heating network.

The head of the energy policy department in the Federal Ministry for Economic Affairs and Energy Thorsten Herdan underlined at the inauguration event that the solar thermal plant of Senftenberg is not a research or demonstration plant but a commercial plant that has been calculated according to economical criteria. As an emblem of the solar district heating technology, the plant will be observed with attention from Berlin, said Herdan. ‘The monitoring of this plant is extremely important to us. Show us with this plant, how it can be done’, called Herdan to the public.

Important facts about the solar thermal plant in Senftenberg
Total area: 2,2 ha
Collector field: 170m * 120m
Gross collector area: 8 300 m²
Number of evacuated tube collectors: 1 680
Total length of the pipes: 6,5 km
Calculated yearly yield: app. 4 GWh
Operator: Stadtwerke Senftenberg
Manufacture and planning of the collector plant and regulation: Ritter XL Solar GmbH
General contractor: INTEGRAL Projekt GmbH & Co. KG, Cottbus

Solar heat in district heating complements classic gas-driven cogeneration plants. The collector field should deliver 80 000 MWh yearly and have a nominal power of 110 Megawatt. It should cover 20% of the heat demand in the district heating network of Silkeborg, and the complete summer load.The plant does not include a seasonal thermal energy storage, despite its dimensions. This leads to especially low heat costs and is enabled by the size of the city of Silkeborg, which has a high enough summer load to use all the solar heat directly when it is produced, explained Christian Stadler from collector manufacturer and general contractor Arcon/Sunmark: ‘We reach here scale effects that we do not know from previous projects. The bigger the solar plant is, the less influence the costs of the connection pipe have on the total costs. One is more flexible when looking for a suitable location.’

The solar plant in Silkeborg is more than twice the size of the until now largest solar thermal plant of the world in Vojens, DK. The 70 000 m² plant there was planned by the international engineering office Rambøll and realized by Arcon/Sunmark in 2015, just like the plant currently under construction in Silkeborg.

Beside gas and solar thermal energy, wind electricity should supply an increasing part of the heat in the district heating network of Silkeborg. Because of the fast wind energy development in Denmark, times with electricity excess and consequently negative electricity prices are becoming more frequent so that power-to-heat, transforming renewable electricity in heat, is profitable.

This article about SDH activities in Bulgaria was publishd by solarthermalworld.org.

Read the complete article here.

First of all, let’s have a look at the solar radiation which has been almost 5% lower than expected (about 1 312 instead of 1 376 kWh/m².year). This situation is linked to the height of the trees which cast larger shadows than what expected during the design phase.

Nevertheless, in spite of this lower availability of ‘fuel’, the measured total yield is 485 500 kWh/year which means a 13% surplus related to the projected yield, calculated to be 429 571 kWh/year. This was due above all to the higher solar efficiency which, in the summer months, ranged from about 45% to 50%. For some months this higher efficiency was caused by the  lower return temperature, if compared with the design value. However, July is a relevant exception: In spite of a solar radiation in line with the design figure and a return temperature slightly higher than the project value, the monthly yield was about 19% more than expected.

In the picture below, the monthly yields are reported by blue lines (‘Atteso’) for the design values and by orange lines (‘Effettivo’) for the measured results.

Source: SDH Energy, Varese Risorse.