Feasibility studies with parabolic trough collector fields in Austria
Between 2021 and 2024 the Austrian Climate and Energy Fund was active in supporting feasibility studies for large solar plants. The fund subsidized 15 studies regarding industrial solar heat plants with a total collector area of 306,000 m2. Among these studies were seven that included parabolic trough collectors to provide heat for breweries at 170 °C, dairies at 140 °C or sausage production at 170 °C. Each report includes a technical-economic assessment of collector fields in two different sizes with a detailed cost breakdown (see figure 1 below). The feasibility studies carried out by the German company Solarlite CSP Technology provide a good picture of what parabolic trough collectors can achieve for process heat in Central Europe. Here, we take a closer look at the report on a plant for the Austrian sausage manufacturer Wiesbauer. All the reports are written in German and can be downloaded here. Photo: Protarget
The aim of variant 1 of the feasibility study for the sausage manufacturer Wiesbauer was to achieve the highest possible solar yield on an existing area in the immediate vicinity of the sausage factory in Vienna. Gas boilers currently generate the annual heat requirement of 22.1 GWh in the form of steam.
The planners from Solarlite determined a possible aperture area of the parabolic trough field of 25,342 m2, corresponding to 14.2 MW of thermal output. On average, around 6,000 m2 of ground area is therefore required per MW of solar thermal capacity. The solar yield in this case covers 40 % of the factory’s annual heat requirement of 22.1 GWh. In variant 2, on the other hand, the authors analysed the economic viability of a much smaller system with 3.3 MW (5816 m2), which can only cover 11 % of the annual heat demand without storage. The simulation calculations were carried out on the basis that the temperature of the inflow to the collector field is 100 °C and it generates steam at 165 °C.
| Variant 1 with storage | Variant 2 without storage | |
| Solar thermal capacity | 14.2 MW | 3.3 MW |
| Aperture area of the parabolic trough collector field | 25,342 m2 | 5,816 m2 |
| Useable solar heat per year | 8.8 GWh/a | 2.51 GWh/a |
| Solar fraction of the total heat demand of 22.1 GWh/a | 40 % | 11 % |
| Specific solar yield per aperture area | 435 kWh/m2 | 469 kWh/m2 |
| CO2 savings | Up to 2,275 tonnes CO2 per year | Up to 650 tonnes CO2 per year |
Table 1: Technical data of the two variants in the feasibility study for sausage manufacturer Wiesbauer. Source: Feasibility study Wiesbauer
The Direct Normal Irradiation (DNI) at the factory is 1,156 kWh/m2 annually. The usable solar thermal yield of the collector field is slightly lower in variant 1 (435 kWh/m2) than in variant 2 (469 kWh/m2) due to the storage losses. The efficiency of the plants compared to the DNI potential is 38 % for Variant 1 and 40 % for Variant 2.
Important factors influencing CAPEX
The total investments for all system components of the two variants are shown in Figure 2. The collector field with the mounting system, balance of plant and piping is significantly more than 50 % of the CAPEX in both variants. The daily storage tank in variant 1 costs EUR 3.2 million, 26 % of the total costs. As neither variant involves an EPC contract for the entire plant but rather a heat supply contract with Wiesbauer, a Special Purpose Vehicle is to be established for the handling and operation of the plant. The costs for this are taken into account at around EUR 300,000 (variant 1) and EUR 65,000 in variant 2 – in both cases 2 % of the total costs.
The two pie charts also show that no economies of scale applied to the collector field. The specific costs for both variants are 156 EUR/m2 aperture area. In contrast, there are considerable economies of scale for the infrastructure. As the costs are virtually the same for both variants, the proportion of infrastructure costs falls from 17 % in variant 2 to 4 % in variant 1.
The economies of scale for project management costs are not quite as high. Here the amount increases from EUR 570,595 in variant 2 to EUR 1,781,500 in variant 1. This is a threefold increase, while the collector field more than quadruples. The cost share therefore falls from 21 % to 14 %.
Figure 1: Comparison of the investment costs for the two variants. Source: Feasibility study Wiesbauer
| Variant 1 with storage | Variant 2 without storage | |
| Solar thermal capacity | 14.2 MW | 3.3 MW |
| Solar fraction related to the total heat demand of 22.1 GWh/a | 40 % | 11 % |
| CAPEX | 12.6 million EUR | 2.75 million EUR |
| OPEX | 201,000 EUR per year | 45,000 EUR per year |
| Heat production costs over 20 years | 77 EUR/MWh | 58 EUR/MWh |
| Annual savings of energy costs | 767,000 EUR/a | 252,000 EUR/a |
| Payback period | 13 years | 9 years |
| CO2 savings over 20 years | 45,500 tonne | 13,000 tonne |
| CAPEX per tonne CO2 savings over 20 years | 277 EUR/tonne | 217 EUR/tonne |
Table 2: Heating costs calculated using the net present value method with a discount rate of 2 % over 20 years, taking into account a CAPEX subsidy of 20 % and a carbon pricing of 100 EUR/tonne. The calculation does not take into account any financing costs, profit margins, risk provisions or general inflation. Source: Feasibility study Wiesbauer
Table 2 clearly shows that variant 2 produces cheaper heat than variant 1,, even if the available space is not fully utilised. Variant 2 without storage amortizes after just 9 years. With variant 1 it is 13 years. In terms of investment costs per tonne of CO2 saved, variant 2 is also cheaper (217 EUR/tonne) than variant 1 (277 EUR/tonne).
Organisations mentioned in this news article:
Solarlite CSP Technology: https://www.solarlite.de/
Austrian Climate and Energy Fund: https://www.klimafonds.gv.at/
Feasibility studies of large solar heat plants: https://solare-grossanlagen.at/machbarkeitsstudien/
