TYPES OF INVERTER
1. Solar Power Conditioning Unit - Solar PCUs are usually installed with off-grid solar installations. It is an all-in-one unit which has an in-built solar charge-controller, inverter and charger, and is connected to a battery bank. The extra energy gets stored in batteries.
2. Solar Grid-tie Inverter - They convert DC from solar into AC and power the connected load. The surplus energy generated can be fed back to the grid if the state has provision for this where net-metering has been implemented. You can get paid for feeding the grid depending on back tariff set by the state Government. However they cannot operate in absence of a grid.
3. Solar Hybrid Inverter - Solar hybrid inverters can function both as ordinary inverters and solar inverters because they can operate on grid as well as solar power. When sun is up and panels generate DC electricity, it charges the batteries through solar power and when the batteries are fully charged, it disconnects itself from the main grid to power the house with solar energy stored in batteries. If the panels are not making enough power to charge the batteries then it takes remaining voltage and current from the grid to make sure that the batteries get charge.
INVERTER EFFECIENCY RESEACH
1. A three years research project examined the most viable ways to make solar PV inverters more cost-effective was concluded in April 2017 by German institute Fraunhofer ISE.
2. The conclusion of the PV-Pack project – conducted by a consortium of SMA Solar Technology, Fraunhofer Institute for Manufacturing and Applied Materials Research IFAM, Phoenix Contact and Fraunhofer ISE – was that to lower costs without impacting power output or performance, inverters built with more highly integrated components were more effective.
COMPONENTS ANALYSIS
1. One way of cutting costs is to optimize the technologies of the components used in lower power classes so that devices with more power can be developed.
2. The components include, on the mechanical side, housing, support structures and cooling components, and on the electromechanical side, plug connectors, inductances and circuit boards.
3. By targeting the“hot core” of the inverter, the cooling and packaging of the inverter could be optimized and the best route towards lower cost without compromising power or efficiency.
4. By uncoupling the cooling element from the housing, we could increase the maximum temperature by 30%, and by sintering materials drastically reduce the amount of material used.
5. By focusing on lowering the temperature of the inverter’s various temperature zones, we could then fit cost-efficient components – with lower temperature requirements – into these new, cooler zones.
6. By using silicon carbide semiconductors (SiC) ,we could increase power density and further reduce material size. SiC has increased switching frequency, and thus enables a reduction in the size of the passive elements in the inverter.
ISSUES WITH PV INVERTER
1. With every 10°C higher temperature of a component, the lifetime is halved. For the relatively cheap inverter, tests at full power revealed temperatures to be 20°C higher than what you would see in an high-quality inverter of the same power class. Applying Arrhenius’ rule, this means a lifetime reduction of 75%.
2. Inexpensive inverter, that produced 30 kW (or 100%) at 20°C, significantly lost output power when the ambient temperature rose above 21°C. At a temperature of 35°C, quite common for solar power plants, the output power degraded to 24 kW. This equals 20% less performance and it got worse with every additional centigrade.
3. The advised DC:AC ratio of 1:1 of the cheaper inverters force plant designers to choose between a reduced array size (reducing lifetime power production) or an increased number of inverters. This also increases installation costs, as well as operations and maintenance costs, and eliminates any perceived benefits of lower inverter cost.
4. A higher DC:AC ratio such as a 1.5:1 ratio increases the lifetime power production and profitability with an significant impact on system design and can actually reduce balance-of-system costs up to 50%.
5. Inexpensive inverters tend to produce electromagnetic interference far above permissible limits of regulation EN 6100-6-3:2011. Peak values were at 65dBµV/m, which is more than 16x the allowable threshold. However, some manufacturers chose to place a “CE” mark on its product.
6. The reasons are most likely due to undersized filters because of the passive cooling concept. Undersized filters are used to generate less heat. This leads to the assumption that the manufacturer has chosen to save costs and thereby created a potentially dangerous environment. Disturbing the radio frequencies is an unlawful act. In Germany, this might be a violation of §315 StGB, which could result in a punishment of up to 10 years imprisonment.
7. Size of the solar inverters depends on the connected load. It is better to keep at least 25% higher capacity of inverter than that of the total power ratings of connected load. Battery sizing depends on the depth of discharge and backup time required to run the connected load in absence of the solar energy or other source of energy (Grid/DG). If the total wattage from solar panels is 1000W or 1kw then you need an inverter of typical ratings of 1000W/1250VA (0.8pf) and a battery bank of 300Ah/24V (7200VAh) capacity.
GLOBAL PV INVERTER REPORT, RESEACH, AND FORCAST
1. The PV inverter market continues to grow more concentrated as it matures. In H1 2016. The top ten solar inverter vendors accounted for 80% of global shipment.
2. Forecasts by greentechmedia in December 2016
i. Demand will fall in the three largest solar markets - China, the United States and Japan - in 2017
ii. Latin America, the Middle East and Southeast Asia will be the fastest growing regions through 2021, with each region expecting annual growth rates above 25% over that time.
3. Market share breakdown of top 20 vendors from 2010-H1 to 2016
Note: Vendors include: ABB, APSystems, Chint Power Systems, Daihen Corporation, Delta Energy Systems, Eaton, Enphase Energy, Fronius, Fuji Electric, Gamesa, General Electric, Ginlong Solis, GPTech, Hitachi, Huawei, Ingeteam, KACO New Energy, Omron, Power Electronics, Schneider Electric, Sineng, SMA, SolarEdge Technologies, Sungrow Power Supply, Tabuchi Electric, TBEA Sunoasis, Tigo Energy, TMEIC, Yaskawa-Solectria Solar
4. Forecasts by Gminsights in Nov 2016
i. U.S. PV inverter market size is anticipated to witness over 14% growth by 2024. Government incentives including tax rebate, subsidy and financial assistance for development of renewable energy technologies may propel the industry growth.
ii. Standalone PV inverter market size was valued over 17 GW in 2015 and in term of revenue is expected to reach over USD 6 billion by 2024 owing to increasing off grid electricity demand.
iii. South Africa was valued over 100 MW in 2015 and in term of revenue is forecast to reach over USD 30 million by 2024. Growing demand reliable and clean energy may favor the industry growth. The Government of Africa has implemented Renewable Energy Independent Power Producer Programs which aims to install 10,000 GWh of renewable energy.
iv. Commercial applications were valued over 10 GW in 2015 and are expected to witness growth subject to regulatory initiatives towards energy efficiency. Growing infrastructure in emerging economies will further boost the demand for PV inverter in future.
v. China PV inverter market share is likely to exceed 70 GW by 2024. National energy administration has announced to install over 18 GW of photovoltaic systems.
vi. Central PV inverter market was valued over 20 GW in 2015 and in term of revenue is likely to exceed USD 10 billion during forecast period. Increasing deployment of commercial and utility solar project may favor the business in future.
vii. Chile is expected to reach over USD 150 million by 2024. Engagement of power purchase agreement with utilities coupled with government incentives is likely to drive the industry. In 2015, Enel green power has signed a power purchase agreement with Endesa for large scale PV project in Chile.
viii. UK PV inverter market share was valued over USD 400 million in 2015 and in term of volume is expected to witness a significant growth over 17% by 2024.
(Source: pv-magazine, sunwindenergy, su-kam, Greentechmedia, gminsights)
