The Technology of Renewable Energy

Hybrid Technology

Technological improvement is a process—there are always flaws to be ironed out and problems to be solved. Renewable energy sources are a good example of this. As we seem to be reminded all too often, inconsistency in supply, a lack of large-scale storage infrastructure, high up-front expenses, grid incompatibility, cloudy days, and even over-generation wane our enthusiasm for transitioning to renewables in the here and now. Consequently, solar, wind, hydro, and geothermal power all tend to be seen as separate, somewhat mistake-riddled entities.

Enter recombination: what hybrid technology aims to do is mitigate each renewable’s flaws by combining it in some way with another technology. Think diversification: a diverse renewable portfolio helps us achieve consistency by taking advantage of a complementary pairing of different energy sources. Although they remain unproven on a large scale in anything but intrigue, these hybrid systems might prove investment-worthy in the near future. This article explores the question of hybrid technologies through the particular example of utilizing the complementary power of solar and wind.

Solar-Wind Hybrids

Solar energy suffers from an innate flaw: during peak electricity usage hours (nighttime) in a typical Californian home, the sun isn’t shining and power from solar is under-generated compared to the demand, while during low electricity usage hours (daytime), the sun is indeed shining and power from solar is being over-generated. Greentech Media outlined ten ways to attempt to deal with this consistency problem, one of which was coupling solar generation systems with wind power to “smooth out” the dips and dives in solar generation.

Since wind tends to peak at night, while solar peaks during the day, the concept is simple—during low solar energy hours (i.e. nighttime), wind power can be imported in place of solar, and vice versa during the day. The U.S. Department of Energy also explains the system’s ability to produce consistent power over the seasons: “In much of the United States, wind speeds are low in the summer when the sun shines brightest and longest. The wind is strong in the winter when less sunlight is available. Because the peak operating times for wind and solar systems occur at different times of the day and year, hybrid systems are more likely to produce power when you need it.” In addition, standalone microgrid solar power requires batteries—often expensive—to store energy for later use, since people need power when the sun is not shining. Introducing wind power as the night-time generator can cut battery costs, as outlined by Sarah Kurtz of the U.S. Department of Energy’s National Renewable Energy Laboratory in this Scientific American article from November 2016. “If you’re in a location where the wind does blow, and especially where the wind complements solar, until the batteries get cheaper than the wind power itself, you’re going to be better off adding wind,” Kurtz says. Additionally, building wind and solar plants in the same location can save money on “grid connections, site development, and approval,” according to Australian Renewable Energy Agency CEO Ivor Frischknecht, speaking on the agency’s recently-financed co-location solar-wind project. These co-location solar-wind projects are, in other words, hybrid systems—where wind turbines and solar plants are in close proximity and connected to the same energy system. Accordingly, Element Power Chief Operating Officer Raimund Grube described his company’s New Mexico hybrid plant as one where “opportunity, land and resource converge.”

However, even a more diversified solar-wind hybrid is not without its drawbacks. Downsides of wind-solar hybrid systems include the potential for wind turbine blades to cast shadows over photo-voltaic arrays in their vicinity, diminishing solar efficiency. An early 2013 study by SolarPraxis AG has helped assuage these fears, however, claiming that loss in a “carefully designed” plant would be minimal—as little as 1 or 2% of total energy output. More importantly, successful implementation of any renewable generation system necessitates fulfillment of a long list of property requirements, maintenance and labor costs, and storage considerations, as outlined here. The normally already in-depth considerations for individual wind and solar systems—e.g. wind resources, vegetation, height, noise, aesthetics, maintenance, cloud cover, existing infrastructure—are made even more difficult when a project intends to overlap the two onto each other.

Solar-Wind Around the World

A couple of utility-scale solar-wind projects are currently being commissioned and tested across the globe. Take the following case study: in June 2014, Indian wind turbine maker ReGen Powertech announced one of India’s first large-scale wind-solar hybrid projects near Coimbatore, some 300 miles from Chennai. The project provides between 200kW-750kW of complementary solar photovoltaic power to the existing 1.5MW wind farm. According to ReGen senior official Archit Khemka, the previous standalone wind energy system generated only about 26% of the maximum output that the plant could be generating if there was always wind blowing. Using the hybrid solar-wind plant, this value went up to 38%, meaning more of the plant’s highest generating capacity was being used, more often. The projected cost of the hybrid plant was about 15% less than that of a standalone solar project with the same megawatt rating.

Updates on the success of the ReGen project in particular are near-nonexistent, but a couple of indicators can point us in the right direction. Firstly, regional government agencies in India are opening up further dialogue regarding hybrid wind-solar systems. These June 2016 drafts from the Ministry of New and Renewable Energy (MNRE) come after October 2015 calls from ReGen for the government to clarify policy regarding the hybrid power plant. Most recently, this November 2016 report identifies two states in India interested in pursuing hybrid technology projects even bigger than Coimbatore: the coastal state of Andhra Pradesh published a draft policy for wind-solar hybrids in August 2016, targeting 3GW by 2020. In late 2015, the state of Rajasthan signed a memorandum of understanding to develop 1.5GW of wind-solar-storage hybrids, with about 500MW to be developed by the end of 2017.

India is not alone in initiating solar-wind hybrid projects. In the UK, green energy company Ecotricity commissioned three hybrid energy parks in 2016 designed to collectively power 1000 homes with 5 MW of installed capacity. These projects come just years after Ecotricity implemented the UK’s first sun-and-wind energy “park” in 2011, which was the addition of a 1 MW “Sun Park” near an existing 16 MW wind farm site in Lincolnshire. In Australia, a $9.9 million grant was recently give to Chinese company Goldwind to build a 10 MW solar plant next to the existing Gullen Range wind farm near Canberra. In November 2016, Spanish wind turbine maker Gamesa—the market leader in Spain and the fourth largest turbine manufacturer in the world—began operating a new 2+ MW prototype combining solar, wind, diesel, and storage, as it looked to cut “off-grid generation costs by 40 percent compared to diesel.”

The fact that the projects around the world are moving forward leads us to believe that hybrid systems are more than just one-and-done trial runs. In India, too, the surrounding states are looking to expand on ReGen’s initial offering, and major news outlets like Ensia, Bloomberg, and Scientific American have picked up Coimbatore’s story. Though empirical evidence is still to come, and a success can’t yet be proclaimed, these projects have shown just one intriguing avenue down which clean energy is traveling. Renewable standalones—wind and solar, among several others—are alive, well, and established. Now, we’re moving forward to iron out their individual flaws, by combining one with another.

 

Image courtesy of Flickr. Originally published by S&S on January 17, 2017.

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