An equitable and reliable solar power grid for farmers

By Praveen Jain, IEEE Medal in Power Engineering recipient

Born in rural India and being at the global forefront of technology over the past 40 years, I can say with certainty that farmers in many countries are not seeing the true benefits of solar power.

Possibly the biggest and best benefit of solar power for farmers is solar water pumps used for irrigation. Powered by sunlight that is harvested through photovoltaic (PV) panels, solar pumps boost crop yield, promote efficient water use and reduce power consumption and greenhouse gas emissions. Off-season, these solar installations can feed power to the local grid, providing extra income for farmers.

Recognizing these positive economic and environmental impacts, many governments around the globe are now implementing new policies to bring these benefits to farmers. For both government and industry, understanding farmers’ real requirements, having access to the best technology and designing innovative products is the need of the hour.

From the farmers’ perspective, these products should be affordable, reliable, safe, simple to use, multipurpose and integrate seamlessly with existing technologies. To achieve these attributes, a number of requirements must be met.

At the heart of any PV installation is the inverter. It should be highly reliable and meet the 25-year life expectancy of the PV panels. If the design life of the inverter is only 12 years, it would need to be replaced at least once. This should be an expense farmers can afford.

The inverter should be multipurpose and compatible with existing technologies, capable of working on-grid, off-grid, with battery inverters and with any type of water pump. Multipurpose inverters help farmers to run water pumps and irrigate their farms, and they enable farmers to earn extra revenue by selling electricity to the grid when their pumps are not in use.

Rural areas often experience frequent power failures and power cuts. More often than not, battery inverters are installed in these areas to provide short-term energy storage to overcome this problem.

There are many millions of already-installed battery inverters and water pumps throughout the globe, representing billions of dollars in total value. New PV installations should be able to work retroactively with the installed base of battery inverters and water pumps. This compatibility would ensure that a farmer who is already financially challenged should not have to spend any more money than necessary for a PV installation.

Looking at the above requirements, a features-rich product needs to be developed, and at low cost. Since the invention of the first power semiconductor switch in the early 1960s, the field of power electronics has gone through a rapid technological revolution. Recent power and control technology developed in this field can be applied in designing a features-rich PV inverter. Many novel nonlinear digital control and lossless switching techniques can significantly reduce hardware complexity by using complex mathematics. Removing physical constraints with the help of complex mathematics can result in a lightweight, compact, cost-effective and features-rich PV inverter that can provide unparalleled high reliability exceeding the life of a PV panel.

Resonant technology can be used in the design of PV inverters to achieve galvanic isolation for increased safety and ultra-high switching frequency operation without causing switching losses. Novel power architecture, based on the resonant topology and nonlinear digital control implementation, can be used to remove the low-frequency power pulsations from the input of the solar panel without the use of large banks of electrolytic capacitors or additional power conversion stages. Together with the converter topology and control method, low-life components such as electrolytic capacitors and optocouplers can be eliminated, and a very high energy extraction efficiency can be obtained.

One other constraint must be addressed. Most of the PV installations required by farmers are small, typically 1 to 5 kW. They also are prone to partial shadowing and dust, which can hamper power production. But these limitations can be overcome with microinverter-based PV architectures. The drawback for farmers is that these systems are more expensive because each panel requires a microinverter.

However, with increasing pricing pressure and growing labor costs associated with installation of the inverters, a new architecture, based on quad-microinverters, has emerged. The quad configuration optimizes four PV modules with a single inverter, simplifying design and installation while reducing the number of inverters required. With fewer inverters needed, the quad microinverter-based architecture brings down the price of installations significantly for farmers, leading to higher output for every investment.

By applying advanced power electronics solutions in the design of new PV products that meet the true needs of farmers, the best technologies become more accessible to them.

Dr. Praveen Jain is Canada Research Chair in Power Electronics and Director of the Centre for Energy and Power Electronics Research (ePOWER) at Queen’s University in Kingston, Canada. His research contributions have resulted in over 600 publications and 100 patents. Dr. Jain (PhD, University of Toronto) is a Fellow of the IEEE, Royal Society of Canada, the Engineering Institute of Canada, and the Canadian Academy of Engineering. He is the recipient of the 2011 IEEE William E. Newell Power Electronics Award, and he is receiving the 2021 IEEE Medal in Power Engineering “for contributions to the theory and practice of high-frequency power-conversion systems” at the 2021 IEEE Vision, Innovation, and Challenges Summit (IEEE VIC Summit) & Honors Ceremony held virtually on 11-13 May 2021.