linear Fresnel annual electric output higher than parabolic trough for same climate input file

Hi Ty,

I've set the fossil fill fraction to 0 across the board and the linear Fresnel output is still 11% higher than the parabolic trough with the other design parameters set as closely as I could.

I do expect a certain amount of losses to happen between the Tnerminol VP-1 and pre-heated water heat exchanger but I don't think that will reduce net annual electric output by 11%.

I suspected the shorter linear Fresnel startup time and lower fraction of thermal power needed for startup were influencing the results, I increased the SAM default values for the linear Fresnel model to match the parabolic trough model values and the difference in net annual electric output fell to 8.2%.

This is getting better but I am still concerned that this result is contrary to what other researchers (Giostri et al, Morin et al.) found using ColSim, ECOSTAR and Thermoflex.

I would appreciate your feedback on this.

Regards,
Jonathan

Hi Jonathan,

The fossil backup, when set = 1, guarantees that the power cycle is producing nominal power by supplying fossil energy when the energy available from the field and storage is insufficient. Thermal storage enables a system to more frequently reach the nominal power output compared to systems without thermal storage. Therefore, systems without storage will use significantly more fossil energy than systems with storage. This additional fossil input allows the annual output of the linear Fresnel system to approach that of the molten salt power tower. The systems with thermal storage will be able to, at times, produce power during the evening (Period 5, where the fossil backup is = 0), which accounts for the higher output of the power tower system.

Your current parabolic trough design is significantly different than the default case in SAM. One SCA is 50 meters longer in your case. Additionally, you include 4 more SCAs in a single loop than the default case. These differences add significant length, and therefore energy, to your SCA loop compared to the default case, which results in significant defocusing. You can observe this by viewing the “field operation factor” in the Time Series results. Is it possible to adjust your field design?

Regards,
Ty

Hi Ty,

Thank you for your reply.

Yes I agree.

Sorry I misread your reply, you're right. Updating the PT collector loops worked a treat and upped the annual output of the PT significantly.

Is the ET150 only 100m long in the SCA library? I can't remember if I changed it to 150m long or if that's the default length. As I understand it, the ET100 is 100m long and the ET150 is 150m long. I could be mistaken but I think that's the case.

Thanks for your help Ty.

Regards,
Jonathan

Hi Jonathan,

I'll reply in case Ty does not have a chance to.

For both parabolic trough models, The default collector length for the EuroTrough ET 150 is 150 meters.

Best regards,
Paul.