Hybrid Solar Wind Power Plants

Hybrid Solar Wind Power Plants

Introduction

 Renewable energy costs have come down, a number of solar and wind power plants added to the system all over the world. Introduction of wind and solar to the system presents some problems as well.  A hybrid i.e. solar and wind at the same site will mitigate some of these issues besides bringing down the cost of this combined power plant. As technology costs come down, combining wind, solar and energy storage looks like the way to integrate renewables at least cost. In most countries legacy generation plants base load, coal or combined cycle gas fire were built by the state. These plants cannot run economically past their operational lifetime. Eventually they have to be replaced with the cheapest, and also the cleanest, form of generation. Wind and solar will replace the lion’s share of legacy generation over the next 20 years or so. Those who recognise this and act fastest will benefit sooner,"

 Number of renewable energy projects that pairs wind and solar to create a hybrid power source is planned. It's a rare combination now, but one that's expected to become more common because of its potential to cut costs while providing a more consistent flow of clean energy

Variations include the combined power generating system by wind mill and solar energy panel. It also includes a battery which is used to store the energy generated from both the sources. Using this system power generation by windmill when wind source is available and generation from PV module when light radiation is available can be achieved. Both units can be generated power when both sources are available. By providing the battery uninterrupted power supply is possible when both sources are idle. Investment per megawatt remains low with weighted average of the individual investments minus land cost plus some additional investment in batteries.

Benefits

The wind and solar energy complement each other. They hit their peaks at different times of day and night, allowing them to provide a steadier output together than if each was alone. And they save money because they can The benefits of wind-solar hybrids start with a simple idea: Solar power is strongest when the sun is brightest, often in the middle of the day. Wind power is stronger at night in many areas of the World  . By combining the two, a hybrid project has the potential to produce power around the clock share equipment, power lines and workers

Solar and wind power suffers from intermittency and variability. In simple words, Sun shines in the day and wind starts blowing in the afternoon and continues till past midnight, but mostly in summers. In western countries, it is the opposite where wind blows hard in winter coinciding with their peak energy demand thus, solar covers one part of the daily peak demand and wind covers the second peak at night hours. In summers, it is handy for us.

 25% of the costs goes into land and transmission which is saved in the hybrid concept. Transmission facilities are under-utilized in case of individual solar and wind plants proportional to their capacity factors – solar 17% of the time and wind about 35% of the time.

Hybrid accumulates it to the sum of the two minus some overlapping portions. Thus, it is not uncommon to get a capacity factor (utilization) of 45% to 55% which is a much improvement.

The consistency is increasingly important as renewable energy partly replaces coal-fired plants or gas fired combined cycle power plants, which can provide 24-7 power, higher hybrid availability will reduce dependence upon fossil fuels. This is valid both at the aggregate level as well as at the local level, where a hybrid properly dimensioned may eliminate the need of flow from the grid, except at rare extraordinary occurrences. .  

Most renewable energy development so far has targeted either the sunniest or the windiest areas, without considering locations that could be good for both solar and wind. That's changing as wind and solar costs decrease and the technology advances. Today, there are many parts of the World. Where both wind and solar can be profitable It will create economic opportunities for wind in parts of the World. Where wind farms are not present . In areas, where wind farms are more common than solar, it's the other way around, with opportunities to put solar panels alongside wind turbines 

Solar-wind hybrid means integration of solar and wind energy production by installing both solar and wind power plants at one piece of land or at nearby plots utilising common transmission facilities.

Solar and wind are not available all the time and require back up generation to dill then gaps, this besides other issues requires flow reversals This needs to be managed .This is important because one of the challenges of managing a power grid is dealing with the intermittent nature of renewable energy.

Power grids have to provide the right amount of power to match customers' power demand moment-to-moment, so natural gas power plants are often kept at the ready to power up when needed. That could include being used on a cloudy day when a region's solar power output is down.

The ability of a gas plant to quickly ramp up and down helps keep the grid reliable . The fossil fuel   plants emit more pollutants per megawatt-hour when increasing or decreasing their output than they do when running at a steady rate. If wind and solar plants built together can provide a more consistent power supply, other power plants could run on a more predictable schedule, with lower emissions and lower costs.

In addition, operators of solar-wind hybrids can save money by sharing assets, wind and solar will be located right next to each other and feed power into the same equipment that connects to the grid, with a single substation. They likely also will share a maintenance building and other operations.

In 2017 Windlab published a study that found one way to avoid excessive curtailment or huge investments in energy-storage capacity in regions such as North Queensland, characterized by very high levels of solar generation combined with a complementary wind-generation profile, is to add more wind. According to the study, even when solar PV only reaches 60% levels of penetration, curtailment levels exceed 45%. A 30:70 solar PV to wind mix would see curtailment levels reduce to less than 10% when renewables penetration levels are at 60%. The study assumes Queensland reaches its 50% renewables energy mix by 2030 target.

If this goal is reached entirely with solar PV, then 50GWh of storage will be required, but if more than half the 50% comes from wind, no storage will be needed. In practice, this means identifying quality high-capacity wind sites, giving wind connections priority and investing in transmission infrastructure to unlock good wind resources, so that wind and solar together ensure a clean, reliable, low-cost network.  But where actual hybrid plants like Kennedy may have a place is in areas that need new capacity and have good wind and solar resources that are complementary. Two generation sources can be connected to the grid for the same cost as a single source, but output is optimized, reducing the levelised cost of energy.

Better use of grid access

India, which has seen a big boom in wind and solar PV installation in recent years, passed a wind-solar hybrid policy earlier this year to make better use of scant grid access points.The Solar Energy Corporation of India launched a 2.5GW wind-solar hybrid tender in June, although it has gone quiet after extending the deadline from August to September.

The US Trade and Development Agency has provided a grant for the technical design and planning of a hybrid project being developed by Indian energy firm IL&FS Energy Development Company Limited (IEDCL) in the state of Andhra Pradesh. About three years ago, IEDCL proposed to the Andhra Pradesh government that hybrid renewable-energy plants would be suitable to support high levels of renewable-energy penetration on the grid.

Preventing curtailment

 Kennedy’s otherwise curtailed output will end up in the battery, which is programmed to either sell electricity into the grid when prices are high — arbitrage — or inject power to provide grid ancillary services, such as frequency regulation. As an example of how lucrative arbitrage is becoming, wholesale prices during the past year have been around A$75/MWh (US$53/MWh).

However, due to high levels of solar penetration in the region, consisting of more than 6GW, of mainly rooftop panels, surplus solar generation is driving wholesale prices into zero territory. As the solar build-out continues, this disparity between prices during peak demand and during periods when solar output is highest but demand is not, creating a surplus, is expected to increase.

Windlab’s existing software covers Kennedy’s dispatch and market operations. As well as supplying the turbines, Vestas has developed the hybrid plant’s software controls that manage all components, including wind, solar and battery, as one integrated and interoperable system. The system knows when to feed power into the grid, when to divert it to the battery, and when the battery needs to release power in response to commands from Windlab’s dispatch and market operations software. Vestas completed its first wind-plus-storage project and wind-plus-solar PV demonstration projects in 2012 to test the concepts and apply other relevant competencies, such as system controls and grid-integration. 

Plants built or planned

  In India, a captive hybrid power plant (HERO) has been installed and commissioned recently. The plant has wind power capacity of 50MW and solar capacity of 28.8MW. With a wind power capacity factor of 28% and solar power capacity factor of 18.7%, the combined capacity factor of the hybrid reaches 41.8%.

Invenergy's Grand Ridge project in Illinois is one of a small number of hybrid power projects to combine wind and solar energy in one site. A larger one with more solar is planned for Ohio.  Invenergy is starting with a 175 megawatt wind farm. Within the wind farm, it plans to build a 150 megawatt solar farm. 

Bloomberg New Energy Finance, which tracks energy developments, also lists small wind-solar hybrid projects in Wales and Chile, among other locations.

In several parts of China & India, there are lighting pylons with combinations of solar panels and wind-turbines at their top. This allows space already used for lighting to be used more efficiently with two complementary energy productions units. Most common models use horizontal axis wind-turbines, but now models are appearing with vertical axis wind-turbines, using a helicoidal shaped, twisted-Savonius system. The Pearl River Tower inGuangzhou, China, will mix solar panel on its windows and several wind turbines at different stories of its structure, allowing this tower to be energy positive.

The Ministry of New & Renewable Energy in India plans to build world’s largest solar-wind hybrid project.. The  project will have a capacity of 160 megawatts and would be built over a land area of 1000 acres. The project is expected to entail an investment of approximately INR 1000 crores ($155 million). The World Bank has agreed to provide funding for the project. The project is expected to have 120 megawatts of solar power and 40 megawatts of wind energy capacity installed and will be equipped with a battery storage system to ensure it remains operational even during nighttime when there is no sun and decline in wind speed.  

Windlab is developing what it says will be the largest utility-scale clean hybrid power plant. When it becomes operational in early 2019, the Kennedy Energy Park will comprise 43MW of wind, 15MW of solar PV and 2MW/4MWh of battery storage. All the components — solar, wind, battery and synchronous generation — are integrated and sitting behind the connection point. To the utility, Ergon Energy, they all look like a single generator. When Windlab started work on the project four years ago, it set out to see how high penetrations of renewable-power generation could be integrated into the grid.

In North Queensland the solar resource is excellent and the wind resource is good in parts, with a capacity factor of about 45%. They are also complementary in some areas. Typically, later in the afternoon, as the sun starts setting, at around 4-5pm the wind starts up and blows until around 9am the following morning

The plant is sited in a fairly remote location, connected to a 66KV cable, with a 50MW capacity. An existing standalone 18MW solar PV plant is already connected. Adding 58MW of wind and solar capacity would have far exceeded the cable’s capacity, resulting in curtailment, especially on occasions when Kennedy’s wind and solar output are both high.

  

Wind, solar sites in Pakistan

In Pakistani wind sites and new technologies, the capacity factor of 45% is becoming possible, giving even better opportunities. Hybrid power plants should have a lower capital expenditure per megawatt as well as lower production cost.

  Hybridisation will be possible in Sindh (Jhimpir and Gharo) and in Baluchistan. Western Baluchistan has many sites where hybridisation is possible due to availability of both wind and solar resources of high quality. Sindh government has announced a 2x 50 MW hybrid wind solar farm at Jhimpir

In the context of Gwadar, this hybridisation possibility may be of special importance. Gwadar today suffers from both lack of water and energy. At present, a coal power plant of 300MW is proposed to be installed.    

Hybrid may also be promoted at kilowatt level in schools, hospitals and other institutional buildings in wind power corridors like Hyderabad and around in Sindh and western Balochistan like Turbat etc.

Ten-to-twenty-kilowatt facilities can be installed at such locations in combination with roof and ground space and its main advantage is almost round-the-clock availability in half part of the year

Policy - NEPRA

The Alternative Energy Development Board (AEDB) in consultation with the National Electric Power Regulatory Authority (NEPRA) and other stakeholders need to announce a policy ..  Also under deliberation is the reverse auction of the projects that has been instrumental in bringing down solar and wind tariff in India and elsewhere. The previous government failed to address this issue   the new administration will have to tackle these issues, the issue is that AEDB has failed to produce documents needed to carry out competitive bidding.

India has released a policy in this respect recently and a captive hybrid project has been commissioned there. In Pakistan also, several investors are examining the feasibility of this useful mode of power generation.  AEDB has already issued 8 licences of solar / hybrid in jJhimpir wind corridor only the tariff mechanism needs to be defined.

System Costs

The Australian government estimated in a 2016 report that integrating solar and wind energy would cut costs by 3 to 13 percent. 

 Other options   

The likely next step for wind-solar hybrids in the broader market is that developers will begin to consider adding wind or solar to existing renewable energy sites Energy storage is also likely to become a key part of the mix as renewable energy projects increasingly operate like traditional power plants.