Microgrid is basically a small-scale power supply network that is designed to provide power for a small community. It can-not be used for high-power consuming devices but can be used as an alternative approach to integrate small-scale distributed energy resources into low-voltage electricity systems. Enabling local power generation, it comprises various small power generating sources that make it highly fexible and efficient.

Basically, the solution aims to electrify houses that are not directly connected to the electricity board power grid due to their remoteness. To be precise, “We have integrated existing hardware components in the market with a powerful embedded system. The setup forms an electricity grid that is small enough to be called a microgrid. This system is powered by renewable energy sources such as solar photovoltaics (PV), wind and micro-hydel. It can be remotely monitored from anywhere in the world,” explains Ganesh Shankar, managing director, FluxGen Engineering Technologies.

Fig. 1 shows the model of the smart renewable energy microgrid.

Fig. 1: Models of houses which form part of the smart microgrid setup at FluxGen Lab From concept to product
Fig. 1: Models of houses which form part of the smart microgrid setup at FluxGen Lab
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From concept to product
“Over 400 million Indians either do not have access to electricity or have intermittent access to electricity. Connecting the whole country to the main electricity grid is a task that would take several years and in some places it may not make an economic case,” points out Hari D.K., chief engineer, FluxGen Engineering Technologies. Distributed energy generation and distribution can potentially solve this problem.

An off-the-grid renewable energy plant connected to a network of houses in rural areas will potentially provide them the same quality of power as obtained from the main electricity grid.

“In India, electricity grid penetration is very poor. Fortunately, the communication network penetration in India is much higher. This makes the case for a smart microgrid whose performance can be remotely monitored and virtually supervised,” says Shankar.

Fig. 2: National Instruments’ Single Board RIO (sbRIO 9641) used to intelligently control and monitor the smart microgrid
Fig. 2: National Instruments’ Single Board RIO (sbRIO 9641) used to intelligently control and monitor the smart microgrid

“We are planning to put our systems in places where there is no electricity. But in case the grid does penetrate, the microgrid should ideally be compatible with the grid for the following reasons:

1. It could optimally utilise grid power and renewable energy power, ensuring that the customers get electricity most of the time.
2. If power generated from the renewable energy source is in excess, it should be able to feed it back to the grid so that other microgrids connected to the network could utilise it,” he said.

Regarding the time taken in developing their concept to product, Shankar says, “Before starting Flux-Gen I was working with GE. There I happened to work on building smart energy meters for about six months. During that time, I got a good understanding of smart grid. After quitting GE, I worked with Selco Solar, a rural electrification company, for about five months. So when I started FluxGen, I wanted to club my experience of working on smart grid to rural electrification so that rural dwellers could have a standard of living as good as an urban dweller’s. Then I decided to pursue the microgrid as I could see the value in it. The whole process duration from inception to working prototype can be estimated as three years.”

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Fig. 3: Solar panels on roof tops of the houses will be the primary power source to the microgrid
Fig. 3: Solar panels on roof tops of the houses will be the primary power source to the microgrid

What makes it different
Microgrid is an idea that has been in the picture for quite some time now. Talking about how their solution differs from the microgrids existing in India, Hari reveals, “There are several microgrids set up in India, but most of them are based on DC transmission. We have developed an AC microgrid system.”

Giving rural houses AC instead of DC will allow them to avail all the facilities an urban dweller could get. Ganesh explains, “Electrical wiring done in the microgrid is similar to that of the main grid, except that it will be connected to lot lesser number of houses. Hence consumers of power from the microgrid will be able to run any electrical appliance that they have.”

Ganesh adds, “While they wouldn’t have much limitation on instantaneous power consumption, the total energy they can get from such a microgrid could be limited based on the size of the plant as the total size of the plant will be limited by the number of solar panels and other energy sources, unlike the main grid which, technically, can give you any amount of electricity you are willing to buy.”

Standard solar energy systems are available as autonomous systems that are connected to a single house. However, there is an inherent advantage in pooling (like car-pooling) that is leveraged by a microgrid to deliver electricity to several houses.

“For example, one of the components of a solar PV system is the inverter, which converts power from DC to AC. Suppose an inverter of 1kVA size (rating) costs Rs X. Then, a 10kVA inverter for a pooled system would not cost 10X but closer to 3X. Also, 1kVA inverters would have power conversion efficiency of about 80 per cent, whereas a 10kVA inverter would have an efficiency of 95-98 per cent,” explains Shankar. Thus there are cost and quality advantages to having a microgrid solution over independent systems (refer Fig. 2).

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How it works
Ganesh and Hari explain the working by referring to Fig. 1. Basically, the entire system or solution consists of energy consumers (individual houses) and an energy generation setup. Individual houses are connected to the power network via a smart meter, which can communicate with the generation end. One of the main components used in this solution is the solar PV panel. It is placed on the rooftop of every house. Another vital component is the solar converter, which performs three tasks. It charges the battery from solar power, converts the DC power from solar or battery to AC, and if the microgrid is connected to electricity board (may be in the near future), then feeds the excess power to the main grid.

 

Why DC microgrid is less effective than AC microgrid
1. Household appliances like bulbs, fans and television sets are commonly available with AC power as the input, whereas getting the same in DC format is difficult. If one is still able to get a DC system, it will cost more than the AC system.
2. Also, AC products are more evolved, as they are manufactured by leading electronics companies. Though AC power is converted to DC in most systems, opening up a system just to trace the DC point is not feasible. DC utilities are not scalable in the Indian market.
3. Power dissipation (resistive loss) in AC wiring is much lesser than in DC wiring. For houses in the vicinity (in a DC microgrid), this could lead to reduced overall system efficiency. In our case study, we could do a calculation for both the systems and get the exact figures.
4. The efficiency of inverters increases with power capacity, while the cost reduces. For instance, one can get an inverter with 6kW power capacity and an efficiency of more than 90-95 per cent at three times the price of a 1kW inverter, which will have an efficiency of about 85 per cent. For a microgrid with more than ten houses, the peak power required would be about 6 kW. If those ten houses are powered with DC power, the cost and efficiency would perhaps converge with AC power.
5. Also, during some emergency or maintenance, a diesel generator set (an AC power source) can be connected to the system in order to ensure that the consumer is not deprived of power.

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Contributed by: Ganesh Shankar & Hari D.K.

The battery incorporated in this so-lution stores the solar energy to power the house when there is no sunlight. The feature of Energy and Health Monitoring system monitors the plant operation and ensures the plant is operating in the limit of safety and gives an alarm if it is not in a safe health condition. This feature enables preventive maintenance of the plant. The most important aspect of this solution would be to tabulate the energy consumed by each individual house and also communicate the energy and health data to the remote location via Internet. For this there is a communication module that communicates with the individual meters. This helps the plant operator to virtually monitor the performance and health and also control the plant with an internet connection, while being located anywhere in the globe.

Fig. 4: Digital meter used for energy monitoring and communication at individual houses
Fig. 4: Digital meter used for energy monitoring and communication at individual houses

The smart meter can measure the electrical parameters and can also connect or disconnect power according to the operator’s instructions, and it can communicate with the communication module continuously. So the power and meter communication network forms the channel for power transfer from the generating point to individual houses. The communication network could be wired or wireless based on the geographic spread.

In the future
Depending upon the geographical location of various other renewable energy sources such as wind, micro-hydel or biogas, this system can be integrated with solar as the primary source.

“If in case the electricity board extends the grid, then it can be fitted to the microgrid seamlessly. Diesel generator can also be integrated as a contingency plan (for power when there is emergency or during maintenance),” says Hari.

Ganesh informs, “The first version is ready. Based on the feedback we get from the initial takers, we will implement more features. A fully functional working prototype is ready in our lab and we are looking forward to work with government bodies, NGOs, international bodies, private setups and social enterprises in building as many smart renewable energy microgrids as possible.”

Adding to that, Hari says, “We wish to sell the smart renewable energy microgrid tools to government, NGO or private setups who will operate the system using the tools we have developed for the operation of a microgrid. We will also sell them billing software, which will help them to collect appropriate charges from the individual power consumers of the microgrid.”


The author is a tech correspondent at EFY Bengaluru

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