Sustainable power generation through renewable energy, instead of conventional fossil fuels, not only helps to reduce our carbon footprint but also makes power available to non-electrified remote areas. Since renewable energy sources like solar or wind are not available in all seasons, it is not advisable to rely on them completely. For example, solar energy cannot be harnessed to its full potential during the monsoons, while wind speeds may be high in one season and not so in another. In areas where more than one renewable energy source is available, a hybrid power system that combines their benefits can improve the reliability and stability of the grid.
By Ayushee Sharma
Wind-solar hybrid systems interface wind turbine generators with solar panels to generate power in a decentralised mode, typically in the range of 1kW to 10kW. These standalone systems are connected to a charge controller that can handle both systems for charging
the battery, so that energy can be used whenever needed. A compatible inverter converts common DC output to AC for purposes like power distribution, powering appliances such as
a refrigerator and oven, and so on. AC outputs from the two systems are fed to a common bus, and control equipment regulates the output power of the system. In case of on-grid hybrid systems, the battery is charged by the grid when both solar and wind power are not available. The configuration is done such that the individual systems can easily function at the same point of grid connection. These systems can be installed on rooftops if their size permits. The cost varies, based on the ratio of wind and solar components, and may be even cheaper than a solar system. Depending on which renewable source’s power generation capacity is higher in a region, the size of that system, wind or solar, is bigger.
Generation of power from wind energy is done by wind turbines (commonly on a vertical or horizontal axis). The blades of these turbines rotate with wind blowing within the range of defined cut-in (usually, a minimum of 4-5m/s) and cut-off speeds, coupled with generators.
The turbines’ axis of rotation must align with the wind direction. Solar power systems have solar panels that consist of photovoltaic (PV) cells that use sunlight to generate electrical energy. Factors like sunlight intensity and duration, as well as the cleanliness of the panels and their orientation, need to be considered for efficient solar panel arrangement. Some installations have solar panels that rotate in alignment with the movement of the sun across the sky, so that they receive more direct sunlight throughout the day.
Storage devices can improve the output consistency of these systems, increasing reliability and ensuring uninterrupted power supply. The size of the battery is also smaller in hybrid systems, which makes it easier to handle.
| Expert opinion |
| Wind-solar hybrid systems can be used in a variety of areas (depending on the availability of the natural resources), such as commercial and industrial microgrid projects, as well as for power supply to residential areas and to places that suffer from power shortages. Based on the system load and the specific requirements of the project, the total investment for a wind-solar hybrid system is between US$ 50,000 and over US$ 1 million. The payback period ranges from three to eight years, depending on the natural resources, local electricity prices, and government policies. The investment required for wind and solar streetlight systems is generally around US$ 5,000. Our company, UGE International, is a world leader in Darrieus vertical axis wind turbines (VAWTs). We work in several renewable energy areas like vertical axis wind power generation equipment, wind-solar complementary microgrid systems, wind-solar complementary street lighting, commercial distributed renewable energy, etc. The economics of a project and policy support are the biggest challenges in this field. Government subsidies greatly affect investment returns. —Junfei Liu, director of operations, UGE China |
Hybrid systems are often used for small loads. In the residential sector, there has been significant adoption, particularly in single-family homes, luxury apartments, and large multifamily buildings to fulfil a definite set of power requirements. In the commercial and industrial sectors, hybrid systems can be used in places with chronic power shortage or where the grid has not reached, like rural offices, schools or small hotels. These systems can address basic needs, as only a few loads like fans and lights have to be powered. Due to this, standalone hybrid systems are generally preferred over on-grid systems.
Other application areas include the military and railways. According to a report from HTF Market Intelligence, the global wind-solar hybrid systems market is expected to reach
US$ 1.5 billion, growing at a CAGR of 8.57 per cent between 2019 and 2025. The Indian Railways is already issuing tenders to implement wind-solar hybrid projects.
In spite of the potential of hybrid systems, the high initial investment, the long payback period and uncertainty about their applicability have made people sceptical about their viability, thereby preventing more widespread adoption as an alternative to fossil fuels, across the globe. Several companies in India, however, are working on wind-solar hybrid systems. These include Supernova Technologies Private Limited, Zenith Solar Systems, Alpha Windmills,
Unitron Energy System Pvt Ltd, and ReGen Powertech Pvt Ltd. Many regions in India have the potential to harness both wind and solar energy on a medium to large scale.
Often, individual wind, solar and storage systems are located at different places and require proper transmission infrastructure across all these locations. This results in extra costs and inefficient utilisation of infrastructure. India’s Ministry of New and Renewable Energy (MNRE) has introduced the National Wind-Solar Hybrid Policy to promote large scale wind-solar hybrid power projects. The policy encourages technological advancements and optimal utilisation of transmission infrastructure. Individual solar and wind power plants can also be converted to hybrid systems, as long as owners pay the charges for additional transmission access. The power generated from hybrid projects can be sold to third parties, who must then fulfil the renewable purchase obligation (RPO). This is done to increase renewable energy demand in the country and achieve the target of generating 175GW of power using clean energy sources, by 2022. Following the guidelines for the bidding process and tariffs, the Solar Energy Corporation of India (SECI) entered into a power purchase agreement (PPA) with Mahoba Solar’s parent company, Adani Green Energy, in 2019. The project is scheduled to be commissioned in 2021-22. Apart from this, a PPA with SBE Renewable is also scheduled to take place soon.
Outside India, too, various initiatives are being taken to boost the sector. Gamesa, Blue Pacific Solar Products, Grupo Dragon, and Alternate Energy Company are some of the popular names in this field. In 2019, the Kenyan Investment Authority and the Meru
County Government entered into a Memorandum of Understanding (MoU) with Windlab and Eurus Energy for the development of the Meru County Energy Park, the African continent’s
first large scale wind-solar-storage hybrid project. The aim is to produce up to 80MW of clean energy to power homes, and construction on this project is expected to begin in 2021.
