Solar Power molten salts, fixed number of heliostats

Hi!

I'm student from Spain and I'm working on my degree final project.
I used SAM to simulate a certain CSP parabolic through plant and now I have to explore the feasibility of other CSP technologies based on data of the inicial plant.

What I need to do now is to compare the results (LCOE, anual production, capacity factor, etc...) obtained for a Power Tower molten salts plant, when the reflective area is constant and fixed, and equal to the one in the original csp through parabolic plant.

What I did was trying different solar multiples until one gave me the desire heliostate reflective area after pushing the optimizarion button. I also ran a parametric analysis with different solar multiples, and made sure the value I introduced minimized the LCOE. Up to this point I considered no TES and I did not permit more optimizations as that would have changed the number of heliostates which I need to keep constant.

My problem is, when running another parametric analysis considering 2 hours of TES (with no optimization), the solar multiple I assumed was valid from the first analysis gives me a LCOE which is lower than before. That makes me think I'm doing something wrong, as it makes no sense to me: the solar multiple that minimized the LCOE with no TES can't give me a lower LCOE if I implement TES, it should provide a greater value.

I'm a bit lost, as I can not figure out how to make a correct analysis with logical results, keeping the reflective area always constant.












assign a certain number of heliostats for the CSP Power Tower molten salts

Dear Raquel,

I am not sure what is causing this unexpected result.

One possibility is that the factors on the Time of Delivery Factors page are causing the unexpected results you are seeing. To model a project with a constant PPA price, be sure to choose the "Uniform Dispatch" schedule from the library, and set the value of the TOD factor for Period 1 to 1. Otherwise, the PPA price for power generated at night is different from the price during the day.

Best regards,
Paul.

Hi Raquel,

Just out of curiosity, did you get resolve this?  I know the post is more than a year old but it would be of interest to me to know what the outcome was of this unexpected result.  The reason is that, if I understood correctly what you are trying to model, I think the result should be expected.

You say: "the solar multiple that minimized the LCOE with no TES can't give me a lower LCOE if I implement TES, it should provide a greater value."  I don't think this is the case... the LCOE should come down because the power unit which has a capital cost is being better utilised.


I built an alternative model to SAM in order to compare current state of the art with a new concept in collector/receiver configuration I'm working on.  I wanted to compare like for like so, rather than starting from the power unit and then applying a solar multiple, I targeted a 90% capacity factor and sized the rest of the components to suit (thermal storage, generator etc). What was interesting was not only to see a drop in LCOE across the board but also the difference in drop between the different technologies. in both my concept, and power tower, the drop in LCOE was in the order of 45 - 50% whereas with parabolic trough it was only 22%. The reasons are the balance in costs between the components of the system

- The storage added to the cost of the installation but it meant that the power unit could be significantly smaller while the same overall amount of salable electricity was produced.
- Because, for power tower, thermal storage is cheap relative to the power unit (when compared to parabolic trough), the cost savings from being able to use a smaller power unit are higher so the LCOE comes down more significantly with storage.
- What is interesting was to see how my design compares... I am looking at lower overall efficiency of the system but with cheaper energy capture costs ~$70/m2 collector and higher concentration ratios (~4,000 to ~6000 range). This allows me to target higher temperatures, which allows me to significantly drop the per watt cost of the power unit. It should also allow me to drop the storage costs but I still have to assess that so have kept the same per kWht costs as with power tower. This means that the ratio of the cost of storage to cost of power unit bumps back up to that of the parabolic trough and yet increasing the capacity factor still produces a drop in LCOE similar to that of a power tower... hmm.
- I concluded that, while the LCOE / capacity factor relationship is primarily dependent on the storage/power unit cost ratio, one has to relate it all back to the capture costs: As the capture costs come down, the impact of this storage / power unit ratio becomes more significant in overall economics.

All that said, this leads me to conclude that your observation could be correct and if it is then all CSP plants should be built with storage for 24/7 operation.

Regards,

Andrew