Facing the Operational Challenges of Mini-grids

Overview

The following article details the proceedings of the Micro Perspectives for Decentralized Energy Supply Conference - 2013. The experiences from projects in India, Nepal and Tanzania using mini-grids to extend access to electricity for local communities are detailed.

Analyzing Drivers and Barriers for Renewable Energy Integration to Small Islands Power Generation – Tapping a Huge Market Potential

By Enrico Howe - Reiner Lemoine Institut

Introduction and Motivation

This presentation discussed findings on how socio-economic and natural factors have influenced the introduction of renewable energies to island electricity grids. Financial, market, policy and natural factors are studied in order to analyze which of them could be drivers or barriers for successful technology specific renewable energy implementation to islands. The existence of a regulatory framework, using e.g. a feed-in tariff, is the most important for the large-scale implementation of young renewable energy technologies as PV and wind energy. Furthermore a spatial Geographic Information System analysis of global islands is carried out to describe area, location and population of the islands.

Methodology

There is a special remark on the market potential of global islands as well as on the socio-economic factors. Until now, island grids are mostly supplied by diesel generators which results in both high CO2 emissions and high electricity tariffs. The renewable energy resources on islands are very good even in some pacific islands geothermal energy could be used.

Indonesia and Philippines have the densest population, while on less than 10,000 islands live less than 10,000 inhabitants.

The analysis took into consideration:

• Independent and semi-autonomous island states
• No base load power plants
• No grid connection
  
• Highest population < 3 Mio. Inhabitants
  
• Max. 2 GW installed capacity

Considering the socio/economic factors: GDP, competition, ownership (private or not), regulatory framework, energy vision), analyses were carried out for the specific scenarios (only PV, only hydro, only wind, all RE, only new RE) were developed and analyzed.

Results

• Each scenario has (at least) one very good determinant
• There is a big spread of variation
• Feed-in tariff programs are highly recommended
• 87,000 islands with 11,300 inhabitants were examined
• Hydro is not affected so much by socio/economic factors

A Community Managed Micro-Hydro Connected Mini-grid in Nepa

By Bhupendra Shakya - Renewable Energy for Rural Livelihood Programme AEPC

Introduction

Despite Nepal has a high hydropower potential and enough Renewable Energy sources, there are still many people in rural areas that do not have access to electricity. This presentation focused on Micro-hydropower systems (MH) and on the innovative concept of a community managed micro hydro system connected as mini-grid, which was established as a pilot project in Baglung, Nepal. The current technology allows to run parallel six Micro hydropower plants (MHP). A cooperative has been created for the sustainable management of the system.

Motivation

The investigated region is located between China and India. The potential of hydro-power in this region comes up to 83 MW, of which only 1% is used. Nowadays, there is still a high dependency on oil and other traditional energy sources. 56% of the population has access to electrification. The Ministry of Energy responsible for the grid extension does not have rural electrification as a priority. Different organizations such as AEPC (Alternative Energy Promotion Centre) have provided support to off-grid-systems.

10% of the population was connected to the grid thanks to the RERL-Program (Renewable Energy for Rural Livelihood) that was founded in 1996, covering 31 out of 75 districts. The parsed households are far away from the grid or neighborhood.

Hydropower plants with less than 100 kW are categorized as micro hydro and deploy in regions with available water resources and suitable terrain, accounting with an installed capacity of 22 MW.

Challenges

Main Problem: The energy supply was not reliable during supply period. Lighting is, in many cases, the only use of electricity. A threat to the micro hydro plants is the expansion of the grid, which implies a waste of resources as the MHP are likely to be abandoned as soon as the grid reaches the region.

Results

An interconnection between the mini-grid and the national grid was established, by offering a sizable load to the NEA (Nepal Electricity Authority). The surplus electricity of one/more MHP is balanced with the deficit electricity of other MHP. In order to assure system sustainability, the revenues of the MHPs are increased from the high use/sale of electricity.

In the Baglung Mini-Grid Project, 6 MHP are connected to each other, with a total capacity of 107 kW providing services to 1200 households. The management of the plants is community based, while MHP functional groups out of community organizations are present, making the project financially viable. A microprocessor based control system synchronizes various MHPs and manages the connection to the national grid.

The use of the MHP brought a sense of unity to the community and a high sense of confidence to own and manage bigger projects by having not only technical and social advantages, but also economical.

Overcoming Grid Instability in Micro-grids by Using a Flywheel Energy Storage System While Operating a PV/diesel Hybrid System

By Martin Baart - ABB

The third presentation was cancelled and Mr. Martin Baart from ABB held a spontaneous presentation.

Introduction and Motivation

The so called Marble bar hybrid system is installed in a remote Australian area. Australia has a regulatory framework which obligates the utilities to provide the same quality of power with no exception between urban or remote areas.

Since there are some technical projects being carried out in Marble Bar, the need of stable power was the huge challenge. Thanks to a lot of space available, a 300 kW PV system with single axis tracker was installed and combined with 4 x 320 kW diesel generators and a 1 x 500 kW power store grid stabilization device (flywheel energy storage).

Challenges of the System

• The system is used on a daily basis.
  
• When the generator load is set for operation, it cannot be changed often.
  
• The combination of PV and Diesel requires limiting the power of the PV system.
  
• The surplus of the PV plant has to be limited in order to operate the diesel generators in safe conditions. Not limiting the load would drive the generators as motors.
  
• Thermal plants have lower fuel efficiency.
  
• Necessity of back-up for the case of cloud-covering (no power from PV).
  
• During operation, frequency and voltage are measured in order to assure stability through the flywheel control. The flywheel storage system can switch in 5 ms from 100% energy absorption to 100% energy rejection.
  

Results

PV-systems are not a stable source of power, even in sunny days. There have been cases, where there was no cloud coverage at all, but the PV-power was not maximum due to air-particles that cannot be seen by humans.

The construction of the generators demands their operation within 15-30 % of their total power at least, which implies that the PV-system can never be used to 100% capacity.

The frequency is constantly changing; it can fluctuate around off-grid systems with no need to be around 50 +/-0.2 Hz.

3.4 Q&A

1. What could be said about the price of the whole system? It is hard to say, prices depend on the size of the system, the required capacity and used technology.
2. Has this system been used in combination with other RE-sources? There has been a solution for hydro-plant in the Atlantic, the hydro-generators were able to run for 5 days in a row.
3. Spinning reserve is needed to ensure a failure of the plant can be covered (since there is volatility in the RE-source). Two diesel-generators are the minimum needed, even if only one of them is in use, the other should be a back-up.
4. Why is the load of the system so high (2 MW)? The research-basis needs a huge load. Even though it is critical to have RE-sources for a stable supply, this system could perform well enough.

4. Open Discussion and Questions

1. Are there common regulatory frameworks on islands? The regulatory frameworks on islands are crucial for the deployment of RE, but they are related to the countries. Semi-autonomous countries have a strong link to their former colonial countries and most of them use feed-in tariffs.
2. How big is the influence of regulatory frameworks in reality, for example in Nepal? In Nepal there is no feed-in tariff existent. Due to this, there are technical solutions for cooperation.
3. The utilities have to take care of power quality.
4. Does a framework for the framework exist, something like an international overlook from all countries? Not exactly. IRENA (International Renewable Energy Agency) exists and advices countries in policies setups or prevent mistakes while regulatory frameworks are being developed. Caribbean islands for example have a strong influence from the US. In addition, frameworks help to develop better business plans for RE.
5. Difficulties in financing huge projects? Two points of view: (1) People have the money and invest because they know that the system in going to be paid. (2) Small communities that need the energy supply are mainly financed by NGOs and third parties.
6. Suggestion of ABB to the control system used in Nepal: control the valves by the load differences.
7. Are there any problems concerning the paying strategy/financing in Nepal? No, the project is financed by the people who are paying for the electricity.
8. Outlook of the Nepal project: follow-up projects without the need of financial support from the outside.
9. Gradual shift to community credits, no tariff by connecting to main grid.
   

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