The following questions derive from Task 54's Solar Academy webinar on March 14, 2018. If you wish to enhance this list by one of your questions, please get in touch with us.

 

Will the webinar presentations be available on the ISES website?

Slides were available only for 24 hours and then transferred to a restricted area with access for ISES members. For a recording of the webinar, please visit our SHC Solar Academy homepage.

 

Will it be possible to have the detailed excel template of the LCoH calculation you presented during your webinar on 14th March 2018?

We are currently working on preparing a user-friendly excel sheet for the calculation. This will be available online twoards the end of Task 54 in autumn 2018.

 

Is LCoHs calculated in the same fashion for solar thermal plants? What would be the changes to implement in comparison to residential LCoHs?

Basically, the equation can also be used for this purpose but for solar thermal plants you might have to consider taxes and depreciation. Please have a look at our info sheet for the more general equation.

 

In the LCoHs, was decommissioning taken into consideration? What are the costs related to recycling the collectors?

It was considered equal to 0 as to our knowledge we do not know any study which could allow us putting a price on the remaining materials.

 

For the LCoHs, how do we include the cost of heat pumps if this is required? And how can this be compared to other systems that do not require a pump and only rely on natural diffusion of heat?

In the LCoHs you do not include it, it will come in the LCoHo. The method can also be used for thermosiphon systems without problems. However, you need to assess (by simulations or other ways) the saved final energy if talking about LCoHs or the final energy demand for the back-up if you calculate the LCoHo.

 

Based on your example in the presentation on LCoH, solar thermal is not economically valuable compared to a normal boiler system?

In the example shown in Yoann Louvet's slides, the saved energy is slightly more expensive than the energy from the conventional part of the system which contributes to a (small) increase of the overall cost (LCoHo).

 

Is the cost reduction worldwide and in particularly in Africa?

Due to the origin and running projects of the Task 54 participants, reference systems in this Task were only defined for Europe.

 

How do you estimate the cost reduction related to standardization?

The estimation of the price reduction for the investment costs is based on possible reduction due to standardized components and corresponding economy of scales. The price reduction in installation is based on easier to install systems when the components (collector, heat store, etc.) have a certain standard. Finally, systems which are easy to install will be installed without or with less errors, so maintenance costs can be lower.

 

Standardization is definitely an answer to cost reduction, could you tell us more about vertical integration of solar thermal applications? Is there a way to reduce costs by integrating each individual part of the value chain?

Yes, the highest benefit of standardization could be achieved in the case when standardization penetrates the complete value chain, starting from the production of semi-finished parts, components and interfaces up to the installation and maintenance.

 

How will you coordinate the standardization with many manufacturing companies having IP that they do not share with competition?

This is indeed a problem and the work includes a lot of compromises. In the first stage, we will not have a standard including all different dimensions. However, we are about to agree on e.g. the collector connection and the interface between collector and mounting system.

 

How would the procedure for the standardization of new solar collector types look like?

This might not always be possible. However, if the new solar collector type is meant for the same application (e.g. SDHW or space heating), the main issues like standardized collector connections and standardized interface between collector and mounting system can be used.

 

How can polymeric collectors by the company Aventa Solar be recycled?

In principle, all parts of the collector can be de-assembled easily without ending up with a material mix. The limit is rather the fact that the material suppliers can only mix a limited fraction of the return material into the new material in order to keep the quality.

 

Conventional flat-plate collectors are almost 100% recyclable and benefit from a long lifetime (over 30 - or even 40 years). What is the situation for polymeric collectors?

This is a complex topic on which quite some work has been done. Further reading can be found e.g. at http://task39.iea-shc.org/publications. See both "Info sheets" by Carlsson et al. and the related paper: LCA with total cost accounting approach comparing conventional with polymeric technology (flat plate collectors and thermosiphon system);

Recycling: "100% recyclable" may be misleading to some extent. During the research for this paper it was confirmed by material providers that only a limited fraction of recycled material can be blend into the production for both, metals and plastics, in order to secure high quality. For a fair comparison, one needs to go into depth. But in principle the statement is correct and also valid for the polymeric collector.

Life time/service life: Many studies were done in IEA SHC Task 39 and the EU FP7 project SCOOP. It was concluded that a service life of 20-25 years is a safe estimate.

 

Are polymeric collectors resistant to hail?

The AventaSolar collector has been certified with the Solar Keymark. In the recent EU FP7 project SCOOP partners from an accredited test institute concluded the standard hail testing (when mandatory) are fully applicable to polymeric collectors (of the present type).

 

A question for Dr. Michaela Meir, Aventa: >1100kWh/m2y seems very good. Is this measured or calculated?

Meant was the solar irradiation on the tilted collector surface per m2 per year.

 

What stagnation reduction techniques can be applied to a medium temperature (150 -250 degree C) XCPC collector designs?

The focus of our work is on temperature limitation in solar systems for domestic hot water and space heating supply (desired limitation to 100°C). In the case of XCPC collectors we see possibilities to provide such a temperature limitation only by using heat pipes. But the type and amount of working fluid inside the heat pipes and many other parameters has to be adapted.

 

How do external factors (such as different climate zones) influence or change the ISFH model for reducing the stagnation temperature (see presentation by B. Schiebler)? Which countries do you focus on in your project?

The presented approaches for temperature limitation are based on switching to higher heat loss coefficients of the collector. Thereby the reachable stagnation temperature is actually influenced by the respective climate conditions. The level of that deviation depends on the concrete technology and aimed stagnation temperature. In the case of heat pipe collectors, the heat pipe design and the amount of the collector insulation can be adapted. The focus of our work is on temperature limitation in solar systems for domestic hot water and space heating supply in Europe (desired limitation to about 100-130°C).

 

What is stagnation temperature?

Stagnation temperature is the temperature the collector reaches under certain ambient conditions (ambient temperature and hemispherical irradiance) when no heat is extracted from the collector by the heat transfer fluid. The so-called standard stagnation temperature is reached at 30 °C ambient temperature and 1000 W/m² hemispherical irradiance.

 

Have you tested or made any research if we combine the system with PV technology?

Such studies are not within the scope of Task 54.