Mini-grid Webinar Series - Q&A

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This page lists all the questions asked during the webinar: Why mini-grid technologies -- PV, biomass, diesel, micro/mini hydro, wind, and hybrid systems -- need to be differentiated.

1st Presentation: Solar PV and Hybrid Mini-Grids - Xavier Vallvé and Pol Arranz

1. Could you elaborate a little bit on "sharing the energy at the village level" challenge that you mentioned. What does it entail? Do you have any recommendation on how to go about this? Technical solutions etc.?

Answer: This question was answered during the webinar and please view the webinar recording for the answer.

2. Where do you source the actual solar technology from i.e. the solar cells/panels for the developing countries - is it usually locally purchased or do you export the technology from Barcelona? Put another way, how does the organization remain competitive when it must have his market challenged by China?

Answer: This question was answered during the webinar and please view the webinar recording for the answer.

3. In this competitive market, how do you size the hybrid system? Meaning, how to optimize the renewable resource to the maximum?

Answer: ​This question was answered during the webinar and please view the webinar recording for the answer.

4. It would be interesting to hear why Xavier recommend flat rate tariff. Why not prepaid?

Answer: ​This question was answered during the webinar and please view the webinar recording for the answer.

5. Is Xavier seeing any breakthroughs in storage costs?

Answer: I do not see a major breakthrough in storage costs but rather better battery management strategies, lower PV module costs, and embedded storage in some appliances that are making an impact on life cycle costs.

6. What is an approximate IRR?

Answer: Since we talk mainly about highly subsidized systems, the overall IRR calculation does not make sense except if we calculate it on the commercial part of the investment, if any.

7. Environmental benefits were not clear. For example, wind in certain cases is considered to have high impacts, what do you think (same for social impacts )?

Answer: Please have a look at the overview table: Mini-grid Technology Comparison.

8. Are there templates/examples available of standardized ESIAs forms that can be shared publically between countries?

Answer: ESIA standards/templates depend very much on the size of the system. Normally for small systems such as what we were talking about (< 100 kW) ESIA is not required.

9. In the mini-grids that Xavier has been talking about, who owns the mini-grids and how do they qualify to be owners?

Answer: Reference was made to several examples in the presentation. Also there are many others in the field. In Ghana for example, the National Government owns the mini-grid and the operation is delegated to a private entity. In Monte Trigo project in Cabo Verde, a private company along with the municipality ows the mini-grid and the operation is done by the company.

10. In Cape Verde they are going for 100% RE, is this possible and what does it mean? Is this for electricity generation? In Cape Verde Wind is the preferred approach...?

Answer: In the Webinar we did not discuss the general national strategy of Cape Verde.

2nd Presentation: Micro/Mini Hydro Mini-Grids - Bikash Pandey

11. How are the people involved in the project and how are the installation operated and maintained over time?

Answer: It is a good practice to involve local people from the beginning in project activities such as: contributing with unskilled help during construction, confirming their commitment to receive the services and their willingness to pay, developing knowledge on how to use electricity efficiently, etc. For operation there are up-keeping and client management activities done by local staff, typically hired from local candidates; skilled electrician maintenance and repair activities is done by part-time staff from the region periodically, along with management and overhead activities. Revenues should at least cover these costs and the cost of replacement of components at the end of their life.

12. When data on river flow is non-existent how do you make an assessment about what flow patterns exist for that river?

Answer: Take flow data from neighboring catchment area where such data is available and transfer it with the ratio of the sizes of the 2 catchment areas. For very small systems, you can take the dry season flow at the end of the dry season as the minimum flow to design the plant (just make a few flow measurements during dry season).

13. Why is it not possible to install a super-extended penstock along the river (for example, from the intake point on this diagram, down to the powerhouse) rather than the usual civils running a leat along the hillside before precipitating the water down from forebay to powerhouse) If the gradient of the river is known to be 1:100 and the necessary head is 3 meters, then a penstock of 300 meters length, installed either in the river or adjacent to the river, would generate the necessary head.

Answer: To have a shorter penstock and longer channel can be cheaper. Sometimes only penstock pipe is used if terrain is easier for pipe and if pipe is cheaper than other alternative. Long penstock pipes can be expensive to be transported to the site.

14. What are the operation/maintenance requirements for these systems? Are they suitable for very remote communities with limited technical expertise?

Answer: Yes, especially for micro/mini hydro O&M can be done locally and often spare parts are locally available. Appropriate for remote areas (see Nepal etc.)

15. Local manufacturing brings down cost but what about the quality of the equipment?

Answer: It depends on the country and the equipment manufacturer; e.g. an Indonesian manufacturer has already delivered a turbine for a Swiss hydropower plant as Indonesia has benefited from an excellent technology transfer program financed by GIZ; manufacturers in Nepal are more focused on Pelton turbines because of high heads. Nowadays even Electric Load Controls are produced in several Asian countries. However, for PV panels and wind turbines local production is rare (see also technology comparison table: "Mini-grid Technology Comparison").

16. How is the capacity limit managed? is it done through circuit breaker(s)

Answer: Yes, sometimes if the resource is really limited then some systems use mini circuit breakers (MCB) so that normal households do not use big machines/appliances. The tariff system normally takes that into account

17. Do you consider the climate change to the available of the water flow? How do you measure it?

Answer: This is an extremely difficult question because the impact of climate change on a small specific site is almost impossible to predict. The general tendency in many regions in the world is that we have to count many extreme events, meaning the dry season becomes dryer and rainy season can bring extreme rainfall. But this is very general and depends on the country. In any case it is more and more important for hydropower to protect the catchment area as “storage” by avoiding deforestation, palm oil plantations and other activities with negative impact on the river regime.

18. How about staffing these mini hydro stations, do they require high skilled workers to maintain and run?

Answer: No, operation and management can be taught to the local villagers. In case of a serious breakdown, a technician needs to be called but many repair activities can be solved easily on site, provided the operators have a decent training.

19. How feasible is it to engineer installations where head height is low?

Answer: “Low head-high flow” systems are always technically more difficult and more expensive than “high head-low flow” systems. In Europe, systems down to about 3 m head exist (ultra-low head) but are maybe technically too challenging for developing countries.

20. With just a penstock and no forebay tank, how do you handle surges?

Answer: Yes, the forebay is needed to balance the flow guided to the turbine.

21. How a community based management team is organized for running a micro hydro system?

Answer: As a minimum you should have 2 operators, 1 book keeper, 1 secretary, 1 manager for systems in the range of < 50 kW; fix a tariff system to at least cover the cost of O&M and make an agreement with the community regarding sanctions for non-payment etc. (rules & regulations); fix the salaries for O&M staff, open a bank account to save money for repair; etc.

22. If the technologies among the renewable energy are needed to be differentiated, does it mean that it is difficult to setup a mini-grid that combines different source of energies? If yes, how difficult/easy is it?

Answer:  If you combine different technologies your investment cost will rise significantly and the system will be technically more sophisticated and difficult to operate (as a general rule!). It only makes sense if it becomes the least cost option for generation.