This introductory webinar explains how a small-scale photovoltaic system works, what is the most suitable solution in your case and, if it makes sense, how to start planning and building your installation.
After a briefing presentation, a case study will be presented using the RETScreen analysis software.
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Q&A Session
By Fernando Nuno / Published on Mon, 2009-01-19 19:52Q: Can RETScreen be used to optimise a design for a given area and also be used if the energy policy is based on imports & exports not feed-in tariffs?
A: Yes, you can run as many scenarios as you wish, then finding the optimal configuration for your particular case. See also the distance between panels in Annex of presentation. RETScreen provides an electricity production estimation. From there you can extract your imports and obtain the net export with the applicable fee.
Q: What should be the tilt angle for pv ?
Depending on latitude there is an optimal angle, which is close to latitude value. You should choose your angle depending on what you need to optimize : winter production, summer production or yearly production. The software provides the production on monthly basis for the various angles you try, then you decide which angle maximizes your function.
Q: Have you considered the effects of performance degradation effects? If so, what are the most important equipment performance degradation processes?
The most important degradation process is relative to PV panels: account 1% per year (loss of efficiency). In 20 years (guaranteed lifespan) the efficiency will be 20% lower. The cause is a loss of properties in materials (glass transmitivity, PV cells efficiency). Inverter can also reduce its performance in the time.
Q: Is the degradation the same for CPV?
www.isfoc.es will be providing this return of experience in the coming months.
Q: How can Retsreen program help me in take the decision?
By providing an expected electricity generation and then an expected return of your investment.
Q: What is the average cost per watt using photovoltaic system nowadays?
For fixed systems should be around 4-5 €/W and decreasing.
Q: How does the ambient temp effect on pv performance?
Account a loss of 0,5% of power per ºC.
Q: PVs generally have a long payback period, how long would you estimate a panels lifespan would be before a replacement would be warranted?
Manufacturer’s guarantees currently run up to 20 years. Current feed-in tariffs allow a payback period around 10 years.
Q: A local installer places panels vertically on the wall of a house. They run cooler and do not accumulate snow. I'm assuming this works well with a low winter azimuth. But will the indirect angle in summer significantly reduce energy input?
You can simulate its behaviour using RETScreen module. Indeed, vertical panels are more optimized for winter generation than for summer.
Q: What about a system in which the bracket does allow for a change in angle for the summer, where the panels block sun from the window (shading the window)?
As RETScreen makes a production estimation on monthly basis you can run each tilt angle for the corresponding months and determine the annual generation.
Q: What is the difference in power output between fixed and Tracking systems?
You can check it by running RETScreen program. Account for 30% in general, provided you have enough direct irradiation, otherwise a tracking system makes no sense.Reply
Complementary Specific Questions Relative to RETScreen Software
By Fernando Nuno / Published on Fri, 2009-01-30 15:31Q: The radiation data from RETScreen are compatable with the data from PVGIS programme?
A: The PVGIS monthly global solar radiation data could be used in RETScreen. It could be entered in the site reference conditions section of the Stat worksheet in the Daily solar radiation - horizontal column.
Q: Can you take into account shadowing effects?
A: Solar shading can be taken into account in the Building envelope form for Energy efficiency projects. It can also be taken into account for Solar water heater for outdoor swiming pools. If you want to take solar shading for other technologies, you could incluide it in the miscellaneous losses as a percentage, or you could reduce the monthly climate data in the Start worksheet.
Q: How to proceed for a new project for a buildind to estimate the right area ? Does RETScreen provide a rule for space between panels?
A: RETScreen does not set a rule, but you can use the Building envelope properties tool in the Tools worksheet to help. For this kind of issue please refer to annex in the presentation above.
Q: Is the manufacturer data up-to-date? Is it kept up-to-date?
A: Yes, it is up-to-date, and we update it regularly.
Q: Is there a program similar to RetScreen that runs natively on a Mac under OS 10?
A: RETScreen does not work directly on Macintosh. However, you can use it on a Mac right now if you use the Parallels software, currently in the Mac OS X and later. We have many users using this successfully. RETScreen is not simply an Excel file, and in fact has close to 80,000 lines of code running it. We will look to eventually have a web-based version of RETScreen which will be platform independent. In the meantime, you can use Parallels.
Q: Does prices indicators exists on RETScreen database ?
A: There is a lot information on costs in the RETScreen user manual. You can find this information in the Cost Analysis worksheeet section, and in each individual technologies sections.
Q: Do you know of any RETScreen Users discussion Group?
A: Not that we know of.
Q: Can RETScreen include energy loss in order to run a tracking system
A: I guess you mean electrical losses. you should include those losses in miscellaneous losses.
Q: Does the programme cater for reduction in efficiency due to lack of cleaning of panels?
A: You can enter this information in Miscellaneous losses
Q: Does RETScreen sofware can be used by an energy consultant company without fees ?
A: yes, anyone can download and use RETScreen free-of-charge. However, the consultant should mention RETScreen was used.
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