Japan had 25.5 GW net capacity (24.5% of world capacity). Reversible turbine/generator assemblies act as a combined pump and turbine generator unit (usually a Francis turbine design). http://www.eia.gov/electricity/monthly/pdf/chap1.pdf, "2014 Hydropower Market Report Highlights", List of pumped-storage power plants in China 1 (Mandarin), List of pumped-storage power plants in China 2 (Mandarin), List of pumped-storage power plants in China 3 (Mandarin), "Electricity Storage and Renewables: Costs and Markets to 2030]", https://www.cia.gov/library/publications/the-world-factbook/rankorder/2236rank.html, "How could pumped hydro energy storage power our future? [25], In 2010 the United States had 21.5 GW of pumped storage generating capacity (20.6% of world capacity). Should a reservoir collapse, the consequences would be limited apart from the loss of the reservoir itself. Inaugurated in 1966, the 240 MW Rance tidal power station in France can partially work as a pumped-storage station. I was thinking about something like that for myself, now i have to figure what size pipe could drain the 5,000 gallon tank in 11 minutes ! Plants that do not use pumped-storage are referred to as conventional hydroelectric plants; conventional hydroelectric plants that have significant storage capacity may be able to play a similar role in the electrical grid as pumped storage by deferring output until needed. Pumped hydro storage plants store energy using a system of two interconnected reservoirs with one at a higher elevation than the other. Among energy storage technologies currently available on a small and micro scale, pumped hydro. Battery installations are growing at a steady clip, but good old pumped hydro storage, which lifts water into elevated reservoirs for later use in generation, still utterly dominates the field. Cost-per-kilowatt estimates for these projects can be lower than for surface projects if they use existing underground mine space. Homerpower - from The Discovery Channel's Homestead Rescue S3 E3 "Hill of Death" Web site for HomerPower - www.homerpower.com China is seeking to build 40GW of pumped hydro capacity installed by 2020.[45]. Thermal plants are much less able to respond to sudden changes in electrical demand, potentially causing frequency and voltage instability. Researchers investigated whether energy storage via pumped hydro … Pumped storage hydropower and compressed air energy storage, at $165/kWh and $105/kWh, respectively, give the lowest cost in $/kWh if an E/P ratio of 16 is used inclusive of balance of plant and construction and commissioning costs. [16] Increased long distance transmission capacity combined with significant amounts of energy storage will be a crucial part of regulating any large-scale deployment of intermittent renewable power sources. Crettenand, N. (2012) "The facilitation of mini and small hydropower in Switzerland: shaping the institutional framework. inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A [3] The round-trip energy efficiency of PSH varies between 70%–80%,[4][5][6][7] with some sources claiming up to 87%. Pumped storage plants can operate with seawater, although there are additional challenges compared to using fresh water. I am available for custom hardware/firmware development. http://www.oregon.gov/ENERGY/RENEW/Hydro/Hydro_index.shtml, http://www.calctool.org/CALC/eng/civil/hazen-williams_g, http://www.reuk.co.uk/Calculation-of-Hydro-Power.htm, http://www.casanogaldelasbrujas.com/blog/2013/01/17/rough-calculations-for-mad-pumped-hydro-idea/, 100 psi * 2.32 foot per PSI * 1 cf/s * 0.55 turbine eff * 0.085 = 10.846 kWatts, 5,000 gallons * 1/7.48 gallons per cuft * 1/1cf per sec = 668 seconds = 11 minutes of power, 10.846 kWatt * 11 min * 1/60 min per hour = 1.99 kWH per 5,000 gallons of water, 100 psi / 2.13 psi per foot * 1 cf/s * 0.55 turbine eff *. As such the energy storage capacity of the submerged reservoir is not governed by the gravitational energy in the traditional sense, but rather by the vertical pressure variation. C is a constant (the value is different in English and metric units). Micro-hydro storage us ing a pump as a turbine is a potentially prom-ising solution in certain cases, for example, for extending existing photovoltaic systems (PV) and thus reducing grid load and enabling economically beneficial self-consumption of the energy pro-duced. Pumped storage hydropower (PSH), the nation’s largest source of grid-scale energy storage, can help solve some of the most urgent problems facing the electric power sector today. IF pumped storage could meet the reserve capacity needs of a 10% reliance on PV & Wind (big IF) that implies the need of 90% being met by the four scaleable baseload sustainable energies above (with minor contributions from Micro-hydro, etc). [18][19][20], Smaller pumped storage plants cannot achieve the same economies of scale as larger ones, but some do exist, including a recent 13 MW project in Germany. The Ffestiniog Power Station (Picture Right) is a 360Mw pumped-storage hydro-electricity scheme near Ffestiniog, in Gwynedd, North Wales. In this paper, following a suggestion made by HOMER Energy (2010), the pumped hydro is modeled as an electrical storage mechanism with a particular capacity and a particular round-trip efficiency. The latest in large-scale engineering technology are variable speed machines for greater efficiency. The need for storage technologies is recently emerging and more discussed on the micro-scale. [50] Several new underground pumped storage projects have been proposed. [21] Also, it is difficult to fit large reservoirs into the urban landscape. If you want to get involved, click one of these buttons! Small (or micro) applications for pumped-storage could be built on streams and within infrastructures, such as drinking water networks[53] and artificial snow making infrastructures. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. The report indicates that the pumped hydro storage identified is 7 times current installed European pumped hydro capacity and is equivalent to 95 million lithium ion batteries of … Suitable sites are therefore likely to be in hilly or mountainous regions, and potentially in areas of outstanding natural beauty, making PSH susceptible to social and ecological issues. These systems may be economical because they flatten out load variations on the power grid, permitting thermal power stations such as coal-fired plants and nuclear power plants that provide base-load electricity to continue operating at peak efficiency, while reducing the need for "peaking" power plants that use the same fuels as many base-load thermal plants, gas and oil, but have been designed for flexibility rather than maximal efficiency. [21] Nevertheless, some authors defend the technological simplicity and security of water supply as important externalities.[21]. Ecole Polytechnique Fédérale de Lausanne (EPFL). In March 2017 the research project StEnSea (Storing Energy at Sea) announced their successful completion of a four-week test of a pumped storage underwater reservoir. At times of low electrical demand, excess generation capacity is used to pump water into the upper reservoir. Low-cost surplus off-peak electric power is typically used to run the pumps. (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||. The relatively low energy density of pumped storage systems requires either large flows and/or large differences in height between reservoirs. Another type of hydro power called pumped storage works like a battery, storing the electricity generated by other power sources like solar, wind, and nuclear for later use. energy characteristics, its long-term reliability and its reduced global environmental effects [2]. The project includes two 60 MW turbines with a maximum capacity of 120 MW and is the first pumped hydro energy in Philippines. The deepest shaft extends 1,406 metres vertically underground. [14] This technique is currently the most cost-effective means of storing large amounts of electrical energy, but capital costs and the presence of appropriate geography are critical decision factors in selecting pumped-storage plant sites. This paper proposes an optimal energy management model for a grid-connected micro-hydrokinetic pumped hydro storage (MHK-PHS) system supplying the industrial load profile. For comparison, a traditional, gravity-based pumped storage capable of storing 20 MWh in a water reservoir the size of a 30 m sphere would need a hydraulic head of 519 m with the elevation spanned by a pressurized water pipe requiring typically a hill or mountain for support. Pumped-storage hydropower (PSH) is a type of hydroelectric energy storage. Along with energy management, pumped storage systems help control electrical network frequency and provide reserve generation. Water is pumped to the upper reservoir in times of surplus energy and, in times of excess demand, water from the upper reservoir is released, generating electricity as the water passes through reversible Francis turbines on its way to the lower reservoir. [44] Existing dams may be repowered with reversing turbines thereby extending the length of time the plant can operate at capacity. These machines operate in synchronization with the network frequency when generating, but operate asynchronously (independent of the network frequency) when pumping. What Bill just pointed out is generally the stopping point. Pumped storage provides a load at times of high electricity output and low electricity demand, enabling additional system peak capacity. These turbines could operate as both turbine-generators and in reverse as electric motor driven pumps. The run off from the turbine goes into a second reservoir and is used to drive a pump to pump the water back up to the top reservoir. [52] Bendigo has the greatest concentration of deep shaft hard rock mines anywhere in the world with over 5,000 shafts sunk under Bendigo in the second half of the 19th Century. In Switzerland one study suggested that the total installed capacity of small pumped-storage hydropower plants in 2011 could be increased by 3 to 9 times by providing adequate policy instruments.[54]. In 1999, the 30 MW Yanbaru project in Okinawa was the first demonstration of seawater pumped storage. [57][58], Type of electric energy storage system using two reservoirs of water connected with a pump and a turbine, "Hydro-storage" redirects here. Figure 3: distribution of pumped hydro energy storage sites identified by ANU. Gross Head x Flow x System Efficiency (in decimal equivalent) x C = Power (kW). At times of low electrical demand, excess generation capacity is used to pump water into the upper reservoir. • The hydraulic efficiency reaches 91% in designed turbine mode. Pumped Hydro Storage Group relies on long tradition of hydropower technology and experience from Sweden and is a proprietary electricity storage solution provider. It is particularly likely that pumped storage will become especially important as a balance for very large scale photovoltaic generation. While StEnSea's test took place at a depth of 100 m in the fresh water Lake Constance, the technology is foreseen to be used in salt water at greater depths. All you need is some water and the means to pump it uphill. In micro-PSH applications, a group of pumps and Pump As T… During. In the presence of sufficient seabed area multiple reservoirs can scale the storage capacity without limits. Taking into account evaporation losses from the exposed water surface and conversion losses, energy recovery of 70–80% or more can be achieved. Hence pumped storage systems are crucial when coordinating large groups of heterogeneous generators. NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Shell Energy has proposed a 5 MW project in Washington State. PUMPED STORAGE. Re: Micro Pumped Hydro Storage A lot of talk is made about pumped water as a method of storing wind or PV power in order to time shift it to peak periods. It has since been decommissioned. Expired - Fee Related Application number US11/509,433 Inventor David C. Heidenreich Dang! It is the only large-scale power plant of its kind. [8] The main disadvantage of PSH is the specialist nature of the site required, needing both geographical height and water availability. The quantity of power created when water is let in grows proportionally to the height of the column of water above the sphere, in other words: the deeper the sphere is located, the more densely it can store energy. The proposed energy storage at the Callio site in Pyhäjärvi (Finland) would utilize the deepest base metal mine in Europe, with 1,450 metres (4,760 ft) elevation difference. The aim of the study is to investigate the behavior of model when minimizing the grid energy costs through power-flow control variables and time-of-use (TOU) tariff scheme. Pumped storage plants, like other hydroelectric plants, can respond to load changes within seconds. It looks like you're new here. [46] A pair of proposed projects in the Atacama Desert in northern Chile would use 600 MW of photovoltaic solar (Skies of Tarapacá) together with 300 MW of pumped storage (Mirror of Tarapacá) raising seawater 600 metres (2,000 ft) up a coastal cliff. [11][12] https://arena.gov.au/renewable-energy/pumped-hydro-energy-storage Electric Energy Storage Technology Options: A White Paper Primer on Applications, Costs, and Benefits. The five largest operational pumped-storage plants are listed below (for a detailed list see List of pumped-storage hydroelectric power stations): In June 2018 the Australian federal government announced that 14 sites had been identified in Tasmania for pumped storage hydro, with the potential of adding 4.8GW to the national grid if a second interconnector beneath Bass Strait was constructed. I did a quick search and didn't see this topic covered. Approvals have been granted for the Snowy 2.0 project, which will link two existing dams in the New South Wales Snowy Mountains to provide 2,000 MW of capacity and 350,000 MWh of storage.[43]. energy storage (PHES) is recognized as one of the most cost-effective because of its predictable. Variable speed operation further optimize the round trip efficiency in pumped hydro storage plants. [26] The EU had 38.3 GW net capacity (36.8% of world capacity) out of a total of 140 GW of hydropower and representing 5% of total net electrical capacity in the EU. [49] Recent examples include the proposed Summit project in Norton, Ohio, the proposed Maysville project in Kentucky (underground limestone mine), and the Mount Hope project in New Jersey, which was to have used a former iron mine as the lower reservoir. The Drakensberg Pumped Storage Scheme, located in the Drakensberg Mountains in the province of KwaZulu-Natal, South Africa, is a unique hydro facility thanks to its use of four dams. As of late 2014, there were 51 active project proposals with a total of 39 GW of new nameplate capacity across all stages of the FERC licensing process for new pumped storage hydroelectric plants in the US, but no new plants were currently under construction in the US at the time.[29][30]. Imagine if we could double Tasmania’s clean electricity generating capacity. Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor It is a configuration of two water reservoirs at different elevations that can generate power (discharge) as water moves down through a turbine; this draws power as it pumps water (recharge) to the upper reservoir. This is a positive development from an environmental perspective, but comes with challenges for the power grid. Pumped storage hydro is a more mature technology with higher rates of round-trip efficiency. Its maturity makes pumped hydro energy storage (PHES) the most used technology in energy storage. Despite ensuring that electric supply securely matches electric demand and in real-time, market, policy and regulatory burdens continue to hinder its growth. Pumped hydro storage is an established technology that has been in operation for over a century, the initial capital cost is very high (mainly due to the civil works of dams or reservoirs), it has higher overall efficiency of around 76% to 85% and a very long lifespan of more than 60 years. When there is higher demand, water is released back into the lower reservoir through a turbine, generating electricity. Pumped storage is by far the largest-capacity form of grid energy storage available, and, as of 2020, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for around 95% of all active tracked storage installations worldwide, with a total installed throughput capacity of over 181 GW, of which about 29 GW are in the United States, and a total installed storage capacity of over 1.6 TWh, of which about 250 GWh are in the United States. This section will explain the methods and considerations used in the creation of a battery equivalent to a pumped hydropower plant. [47][48], The use of underground reservoirs has been investigated. [13] The same pump could be used in both modes by changing rotational direction and speed:[13] the operation point in pumping usually differs by operation point in PAT mode. Pumped hydro storage technology for the modern world - Pumped hydro storage The energy system is rapidly transforming to include more weather dependent energy production. Combining onshore and offshore wind, blades, hydro, storage, utility-scale solar, and grid solutions as well as hybrid renewables and digital services offerings, GE Renewable Energy has installed more than 400+ gigawatts of clean renewable energy and equipped more than 90 percent of utilities worldwide with its grid solutions. To avoid excessive transmission cost and loss, the reservoirs should be placed off deep water coasts of densely populated areas, such as Norway, Spain, USA and Japan. The base of each wind turbine is to be used as a water reservoir, increasing tower height by 40 m and extending tip height to a record-breaking 246,5 m. The lower reservoir for the pumped storage plant lies in a nearby valley, 200 m below the wind turbines. Some have proposed small pumped storage plants in buildings, although these are not yet economical. Using a pumped-storage system of cisterns and small generators, pico hydro may also be effective for "closed loop" home energy generation systems. The Driekloof Dam, Sterkfontein Dam, Kilburn Dam and Woodstock Dam give the facility a generation capacity of 1 GW, and a total storage capacity of over 27 GWh. With a particular focus on storage and pumped-storage schemes". In this regard, a storm-water basin has been concretely implemented as a cost-effective solution for a water reservoir in a micro pumped hydro energy storage. [17] The high non-firm renewable electricity penetration in some regions supplies 40% of annual output, but 60% may be reached before additional storage is necessary. Obermeyer Hydro, Inc. is designing a cost-effective, small-scale, adjustable speed pumped-storage hydro (PSH) system optimized for the energy storage requirements in the United States. During off-peak hours the turbine changes direction and pumps the water out again, using "surplus" electricity from the grid. [13] Such plants provide distributed energy storage and distributed flexible electricity production and can contribute to the decentralized integration of intermittent renewable energy technologies, such as wind power and solar power. The first use of pumped-storage in the United States was in 1930 by the Connecticut Electric and Power Company, using a large reservoir located near New Milford, Connecticut, pumping water from the Housatonic River to the storage reservoir 70 metres (230 ft) above. In certain jurisdictions, electricity prices may be close to zero or occasionally negative on occasions that there is more electrical generation available than there is load available to absorb it; although at present this is rarely due to wind or solar power alone, increased wind and solar generation will increase the likelihood of such occurrences. Evaporation from the upper reservoir has no effect on the energy conversion efficiency, Transmission of electricity between the reservoir and the grid can be established from a nearby, This page was last edited on 13 February 2021, at 03:38. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Capital costs for pumped-storage plants are relatively high, although this is somewhat mitigated by their long service life of up to 75 years or more, which is three to five times longer than utility-scale batteries. Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, wind) and other renewables, or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand. Making use of an existing dam's upper reservoir and transmission system can expedite projects and reduce costs. There are limited opportunities involving suitable underground space, but the number of underground pumped storage opportunities may increase if abandoned coal mines prove suitable.[51]. No mechanical structure other than the electrical cable needs to span the distance of the potential energy difference. The pumped storage powerhouse is a standardised, modular design. Recognize the energy security role pumped storage hydropower plays in the domestic electric grid. • The hydraulic efficiency in designed pump mode is over 80% for wide partial load. When high tides occur at off-peak hours, the turbines can be used to pump more seawater into the reservoir than the high tide would have naturally brought in. thus, It stores energy by pumping water uphill to a reservoir at higher elevation from a second reservoir at a lower elevation. The UK currently (2011) generates about 1.5% of its electricity from hydroelectric schemes. If the upper lake collects significant rainfall or is fed by a river then the plant may be a net energy producer in the manner of a traditional hydroelectric plant. [27] PSH generated (net) −5.501 GWh of energy in 2010 in the US[28] because more energy is consumed in pumping than is generated. The only way to store a significant amount of energy is by having a large body of water located relatively near, but as high above as possible, a second body of water. Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. In pumpedhydro systems pumps shutdown and changeover - are major sources of instability and the complex dynamics and balancing of the ],[7],[8] are major causes of process [6 In this configuration a hollow sphere submerged and anchored at great depth acts as the lower reservoir, while the upper reservoir is the enclosing body of water. The first use of pumped storage was in 1907 in Switzerland, at the Engeweiher pumped storage facility near Schaffhausen, Switzerland. We have 500,000 litres of water in storage 23 metres above a micro hydro pelton wheel. [1][2] The reservoirs used with pumped storage are quite small when compared to conventional hydroelectric dams of similar power capacity, and generating periods are often less than half a day. energy storage pumped hydro Prior art date 2006-08-23 Legal status (The legal status is an assumption and is not a legal conclusion. [10] Variable speed operation further optimize the round trip efficiency in pumped hydro storage plants. However, the overall energy-storage capacity in. Not many places have the geography to support such a solution. Since the submerged reservoir needs only a connecting electrical cable, the depth at which it can be employed is limited only by the depth at which the turbine can function, currently limited to 700 m. The challenge of designing salt water pumped storage in this underwater configuration brings a range of advantages: A current commercial design featuring a sphere with an inner diameter of 30 m submerged to 700 m would correspond to a 20 MWh capacity which with a 5 MW turbine would lead to a 4-hour discharge time. First Gen Hydro Power is investing P6 billion ($124.89 million) to develop a 120 megawatts (MW) Aya pumped hydro storage project in Pantabangan, Philippines. Conventional hydroelectric dams may also make use of pumped storage in a hybrid system that both generates power from water naturally flowing into the reservoir as well as storing water pumped back to the reservoir from below the dam. A recent pre-feasibility study has shown the concept to be viable with a generation capacity of 30 MW and a run time of 6 hours using a water head of over 750 metres. - ARENAWIRE", "China's State Grid to Spend $5.7 Billion on Pumped Hydro Plants", "Massive Energy Storage, Courtesy of West Ireland", "The Mirror of Tarapaca: Chilean power project harnesses both sun and sea", "German Coal Mine to Be Reborn as Giant Pumped Storage Hydro Facility", http://infoscience.epfl.ch/record/176337?ln=en, "Unterwasser-Pumpspeicherkraftwerk erfolgreich getestet", "Is energy storage via pumped hydro systems is possible on a very small scale? [22][23] In the 1930s reversible hydroelectric turbines became available. The most important use for pumped storage has traditionally been to balance baseload powerplants, but may also be used to abate the fluctuating output of intermittent energy sources. Many recently proposed projects, at least in the U.S., avoid highly sensitive or scenic areas, and some propose to take advantage of "brownfield" locations such as disused mines.[9]. Pumped-storage hydroelectricity systems are to be found throughout the world, but always on a large scale. Optionally a pump back powerhouse such as the Russell Dam (1992) may be added to a dam for increased generating capacity. It’s … Deriaz solution is suitable in pumped hydro energy storage at high-variable load. Developers can afford to be very selective since only about 20 sites (the best 0.1% of sites) would be required to support 100% renewable electricity generation. With this limitation the concept would allow for worldwide electricity storage of close to 900 GWh.[55][56]. The potential pumped hydro energy storage resource is almost 300 times more than required. In micro-PSH applications, a group of pumps and Pump As Turbine (PAT) could be implemented respectively for pumping and generating phases. In some places this occurs naturally, in others one or both bodies of water were man-made. Hydropower pumped storage is “astoundingly efficient…In this future world where we want renewables to get 20%, 30%, or 50% of our electricity generation, you need pumped hydro storage. In January 2019, the State Grid Corporation of China announced plans to invest US$5.7 billion in five pumped hydro storage plants with a total 6GW capacity, to be located in Hebei, Jilin, Zhejiang, Shandong provinces, and in Xinjiang Autonomous Region. ", List of conventional hydroelectric power stations, https://en.wikipedia.org/w/index.php?title=Pumped-storage_hydroelectricity&oldid=1006485365, Pumped-storage hydroelectric power stations, Articles with dead external links from May 2020, Articles with permanently dead external links, Creative Commons Attribution-ShareAlike License. PhD Thesis N° 5356. For storage of water for other purposes, see, Note: this table shows the power-generating capacity in megawatts as is usual for power stations. In Bendigo, Victoria, Australia, the Bendigo Sustainability Group has proposed the use of the old gold mines under Bendigo for Pumped Hydro Energy Storage. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.) In open-loop systems, pure pumped-storage plants store water in an upper reservoir with no natural inflows, while pump-back plants utilize a combination of pumped storage and conventional hydroelectric plants with an upper reservoir that is replenished in part by natural inflows from a stream or river. An energy park with multiple such reservoirs would bring the storage cost to around a few eurocents per kWh with construction and equipment costs in the range €1,200-€1,400 per kW. by including seasonal micro hydro systems supported by pumped storage is adding fresh environmentally justified momentum into off-grid power supply in mountainous areas. Pumped-storage hydroelectric power plants, United States Department of Energy Global Energy Storage Database, coordinating large groups of heterogeneous generators, non-firm renewable electricity penetration, List of pumped-storage hydroelectric power stations, http://poppware.de/Storage_for_a_secure_Power_Supply_from_Wind_and_Sun.pdf, "Pumped hydro energy storage system: A technological review", Pumped storage in Switzerland - an outlook beyond 2000, Pumped Hydroelectric Energy Storage and Spatial Diversity of Wind Resources as Methods of Improving Utilization of Renewable Energy Sources, "Variable Speed Is Key To World's Biggest Pumped Hydro Energy Storage Project, China's Fengning Plant", "Reliability of Variable Speed Pumped-Storage Plant", "Pump as turbine applied to micro energy storage and smart water grids: A case study", "Pumped Hydroelectric Storage | Energy Storage Association", "FERC: Hydropower - Pumped Storage Projects", Summary Energy from the Desert - Practical Proposals for Very Large Scale Photovoltaic Power Generation (VLS-PV) Systems, http://www.nrel.gov/docs/fy17osti/67240.pdf, "German grid operator sees 70% wind + solar before storage needed", "German electricity transmission CEO: '80% renewables is no problem, "New record-breaking year for Danish wind power", "Another write-off at the Engeweiher pumped storage facility". Nameplate pumped storage capacity had grown to 21.6 GW by 2014, with pumped storage comprising 97% of grid-scale energy storage in the US. Sorry if it has. Yep, I think your are correct (and I messed up several ways, Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset, Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048