Category Central solar heating plants with seasonal storage

LIST OF TASK VII REPORTS

Tools for Design and Analysis, Verne G. Chant and Ronald C. Biggs, December, 1983, National Research Council, Canada, available as CENS0L1 from Technical Information Office, Solar Energy Program, National Research Council, Ottawa, Canada, KlA 0R6.

The MINSUN Simulation and Optimization Program: Application and UserTs

Guide, Edited by Verne G. Chant and Rune Hakansson, December, 1983, National Research Council, Canada, available as CENS0L2 from Technical Information Office, Solar Energy Program, National Research Council, Ottawa, Canada, KlA 0R6.

Basic Performance, Cost, and Operation of Solar Collectors for Heating Plants with Seasonal Storage, Charles A, Bankston, 1984, Argonne National Laboratories, U. S.A...

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Results

A small minimum of the total annual cost was found in Figure 1, 5 and 6 with the reference costs for the three weather conditions. When increasing the auxiliary fuel cost in Figure 2 the minimum is more marked at around 20,000m2 collector area for a storage volume of 20,000m3 this means a solar fraction of about 80% and for 100,000m3 the solar fraction is 97%.

In Figure 3 the solar collector cost is decreased which only makes big influences on large areas.

In Figure 4 the storage cost is decreased which brings the curves closer together.

The Madison and Copenhagen weather seems to give higher total annual costs compared to Boston although the solar fraction is less as seen in Figure 7, 8 and 9.

Conclusion

The Swedish Application Case Study has not yet been compared with the results from th...

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Analysis Approach

The analysis is mainly done by taking out one reference case after a series of single point evaluations. As there was a striving towards a high solar fraction the reference case with the actual auxiliary fuel cost is not the minimum average annual cost which is depicted in Figure 7.

The reference case is:

collector area

20,000m2

collector cost

247US$/m2

storage volume

100,000m3

storage cost

27US$/m3

auxiliary fuel cost

0.05US$/KWh

weather

Boston

which

had results:

total annual cost

1.45M$

solar fraction

97.1%

Usi

ng

the MINSUN graphing function

sensitivity analyses

the

reference case by varying the

following parameters:

collector area

5-35,0...

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Model Description

Input data values are those recommended by the appropriate IEA task experts, except where specific to the Swedish Case Study.

The weather data used is Boston, Madison and Copenhagen which does not fit very well with the local climate in Uppsala. Therefore the reference case in the simulations has a collector area of 20,000 m^.

A problem with the modelling is that the inlet and outlet pipes in the model are fixed to the top and the bottom respectively. This means that the distribution system will work with an unnecessarily high temperature and that the stratification will be partially spoiled due to different return temperatures from the houses.

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System Description

The solar collectors are centrally located on a field about 500m away from the storage. The collectors are single glazed with one 4 mm thick toughened glass cover and two transparent teflon films underneath. Each collector is 12m^ and the absorber consists of an aluminum plate with a selective layer. The fluid (water/glycol) flows in a copper tube in the middle of the absorber and it passes through 80m of absorber in each collector. The collectors are coupled in parallel.

The storage is a rock cavern with the top situated 30m below ground level. It has an annular form, 75m in diameter and with 30m height. The walls are unlined and the roof Is sprayed with shotcrete. There are two separate systems for inlet and outlet and the pipings are movable as the storage is stratified.

The temperature...

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Swedish MINSUN Application Case Study

Elisabeth Kjellsson
Uppsala Kraftv3rme AB

Gdran HellstrUa
Lund University

Sttren Rolandsson
Studsvlk Energiteknik

Uppsala, June 1983

SWEDISH MINSUN APPLICATION CASE

Case Description

The reference case chosen for the MINSUN analysis Is a real project, the Lyckeho project, situated in the neighborhood of Uppsala, Sweden. The 550 houses in the Lyckebo area are heated with a separate district heating network connected to a solar heated seasonal storage in a rock cavern.

The storage, the collectors and most of the houses have been constructed between 1981-1983. In the Lyckebo project the solar collectors would consist of 30,000 m2 flat plate collectors for 100% solar energy.

This is not the real truth from the beginning as only 15% of the solar collectors are installed and the rest of the "solar ...

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Observations and Conclusions

In general the MINSUN program did perform well. The results seem to be reliable and the program is fast enough to be used for optimization purposes.

In the third section above, some remarks are made concerning some features which are recommended to be included in future versions of the program.

The *manual* optimization method as used in this case is very time consuming. The advantage is that the user can (or should!) follow the optimization process, step by step.

This will certainly enhance the understanding of the thermal and economic performance of such systems.

This will certainly enhance the understand! ng of the thermal arid economic performance of such systems.

S’lOK’ru’.fc volume:

ХП’Н-Ш t из л

г ujulel– м;1 :

АС-7

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Analysis Approach

The purpose of the performance analysis is two-fold:

• to establish and optimize the performance of the solar heating system,

• to test the MINSUN program in its present form, for as far as the system simulation and optimization are concerned.

The performance analysis carried out has been as follows:

First, via best guess and trial and error methods a so-called "Base case" system has been identified. This is the system previously described in the first and second sections above.

After a careful examination of the results with the help of the daily time profiles, the variables for a sensitivity analysis were chosen.

The chosen variables are:

• Collector surface

• Storage volume

• Duct density

• Duct diameter

• Thickness of insulation layer on top of the storage

The performance...

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