- Wind & Solar With Storage Can Power Grid 99.9 Percent of the Time
- Tasmanian Testbed for Large Integrated Renewable Energy Projects Ramps Up
- PV System Values: Solar Energy Needs Electrical Storage Now
- Solar Power Day and Night: New Storage Systems Control Fluctuation of Renewable Energies
- ARPA-E Announces $43 Million for Transformational Energy Storage Projects to Advance Electric Vehicle and Grid Technologies
| 
| Hits: 300
Wind and Solar Power Paired With Storage Could Power Grid 99.9 Percent of the Time
by University of Delaware Energy Research Team
Dec. 10, 2012 — Renewable energy could fully power a large electric grid 99.9 percent of the time by 2030 at costs comparable to today's electricity expenses, according to new research by the University of Delaware and Delaware Technical Community College.
A well-designed combination of wind power, solar power and storage in batteries and fuel cells would nearly always exceed electricity demands while keeping costs low, the scientists found.
"These results break the conventional wisdom that renewable energy is too unreliable and expensive," said co-author Willett Kempton, professor in the School of Marine Science and Policy in UD's College of Earth, Ocean, and Environment. "The key is to get the right combination of electricity sources and storage -- which we did by an exhaustive search -- and to calculate costs correctly."
The authors developed a computer model to consider 28 billion combinations of renewable energy sources and storage mechanisms, each tested over four years of historical hourly weather data and electricity demands. The model incorporated data from within a large regional grid called PJM Interconnection, which includes 13 states from New Jersey to Illinois and represents one-fifth of the United States' total electric grid.
Unlike other studies, the model focused on minimizing costs instead of the traditional approach of matching generation to electricity use. The researchers found that generating more electricity than needed during average hours -- in order to meet needs on high-demand but low-wind power hours -- would be cheaper than storing excess power for later high demand.
Storage is relatively costly because the storage medium, batteries or hydrogen tanks, must be larger for each additional hour stored.
One of several new findings is that a very large electric system can be run almost entirely on renewable energy.
"For example, using hydrogen for storage, we can run an electric system that today would meeting a need of 72 GW, 99.9 percent of the time, using 17 GW of solar, 68 GW of offshore wind, and 115 GW of inland wind," said co-author Cory Budischak, instructor in the Energy Management Department at Delaware Technical Community College and former UD student.
A GW ("gigawatt") is a measure of electricity generation capability. One GW is the capacity of 200 large wind turbines or of 250,000 rooftop solar systems. Renewable electricity generators must have higher GW capacity than traditional generators, since wind and solar do not generate at maximum all the time.
The study sheds light on what an electric system might look like with heavy reliance on renewable energy sources. Wind speeds and sun exposure vary with weather and seasons, requiring ways to improve reliability. In this study, reliability was achieved by: expanding the geographic area of renewable generation, using diverse sources, employing storage systems, and for the last few percent of the time, burning fossil fuels as a backup.
During the hours when there was not enough renewable electricity to meet power needs, the model drew from storage and, on the rare hours with neither renewable electricity or stored power, then fossil fuel. When there was more renewable energy generated than needed, the model would first fill storage, use the remaining to replace natural gas for heating homes and businesses and only after those, let the excess go to waste.
The study used estimates of technology costs in 2030 without government subsidies, comparing them to costs of fossil fuel generation in wide use today. The cost of fossil fuels includes both the fuel cost itself and the documented external costs such as human health effects caused by power plant air pollution. The projected capital costs for wind and solar in 2030 are about half of today's wind and solar costs, whereas maintenance costs are projected to be approximately the same.
"Aiming for 90 percent or more renewable energy in 2030, in order to achieve climate change targets of 80 to 90 percent reduction of the greenhouse gas carbon dioxide from the power sector, leads to economic savings," the authors observe.
| | Hits: 292
Tasmanian Testbed for Large Integrated
Renewable Energy Projects Ramps Up
The A$46 million (US$47.5 million) King Island Renewable Energy Integration Project (KIREIP) developed by state-owned Hydro Tasmania, with the help of state and federal funding, combines a range of new and existing technologies with the aim of reducing the island’s dependence on expensive diesel-generated power. Uniquely, the system will allow for the integration of wind, solar and conventional diesel — eventually to be replaced with bio-diesel – with a giant battery that enables energy storage and smoothing of intermittency without any loss of reliability or grid stability.
“The way these technologies are being used and integrated is world-leading and another example of the clever solutions to real-world problems that have been developed in Tasmania and can be exported globally,” company chairman Dr. David Crean said in a statement. Hydro Tasmania is looking to take KIREIP to other remote and off-grid locations in Australia and around the world.
“Although there are remote area power systems in some parts of the world that are capable of supplying the energy needs of single homes or small villages, this is the first remote system on this scale capable of supplying the energy needs of an entire community primarily through wind and solar energy,” chief executive Roy Adair said in a statement.
KIREIP will deploy Australia’s largest battery, developed by Ecoult — the local subsidiary of Pennsylvania-based battery manufacturer East Penn Manufacturing. Its 3-MW/1.6-MWh UltraBattery has the capacity to power the entire island for up to 45 minutes, enabling Hydro Tasmania to realise substantial savings, Hydro Tasmania’s manager of renewable asset development Simon Gamble told Renewable Energy World.
Invented by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), UltraBattery is an advanced hybrid lead-acid battery that operates very efficiently in continuous partial state of charge use without frequent overcharge maintenance cycles.
Gamble said Hydro Tasmania is currently in discussions with local utilities about providing the integrated solution to other remote communities in Australia, Western Australia and Queensland. KIREIP is expected to provide a good insight into what future grids might look like in 20-30 years, deploying a combination of renewable technologies, backed up by dispatchable power and storage.
Ecoult’s chief executive, Australian John Wood, said the UltraBattery would “shift and smooth” renewable energy generated on King Island and help maintain stability of the power grid. “Ecoult’s UltraBattery solutions support the utilisation of renewable energy by storing energy in periods where there is excess generation and making it available when it is needed to better match demand,” Wood said in a statement.
The island, with a mixture of residential and large commercial power customers — such as a National Foods dairy processing plant — installed its first wind turbines in 1998 in an attempt to head off the crippling cost of diesel. Today, it has a maximum renewable energy capacity of 2.45 MW, which Gamble said the company expects to expand to 6 MW in a couple of years in order to meet peak demand of 3 MW. The shorter-term aim is for the system to meet 65 percent of the island’s energy needs.
Ecoult already has two successful large systems in the U.S., supported by the Department of Energy: a PNM-owned 550-kW solar PV smoothing and shifting project in Albuquerque, New Mexico, which provides variability management directly at the point of generation; and a regulation services site on the PJM Grid providing variability management directly on the grid. On King Island, Ecoult is providing variability management on an island grid.
The company has also successfully demonstrated its technology at the Hampton Wind Farm in the Blue Mountains, near Sydney, one of the largest storage projects in the Southern Hemisphere.
The research links the UltraBattery system with algorithms designed to analyse weather patterns and fine-tune the storage system to the power input that is on the way, which in turn helps smooth-out power supply to the grid. The over-arching objective of the research was to achieve higher penetration of wind and renewable energy in grids.
In the US context, energy storage has just received a boost by “pay for performance”, which means systems such as the one of the PJM Network now are “very strong economic propositions,” Wood said. “You will see an expansion of adoption for box storage into those sorts of applications in the US,” he said.
Wood sees a promising outlook for energy storage solutions on the grid. “King Island will be the model used over and over,” he said. “We are really trying to make the energy storage solution standard and simple for the developer.”
| | Hits: 521
PV System Values: Solar Energy Needs Electrical Storage Now
Why Storage
In 2002 the California Energy Commission Public Interest Energy Research (CEC PIER) funded an investigation into the value of electrical storage combined with PV by Dr. Richard Perez of the State University of New York Albany. This work was intended to address the intermittency associated with PV technology. Intermittency is the reduction of solar output caused by the movement of clouds over PV modules. Dr. Perez came up with the term Solar Load Control (SLC).
A small amount of electrical storage has great value for grid-tied PV. For commercial buildings with PV, small amounts of storage can ensure a demand reduction value on the utility bill (a similar demand reduction can be obtained from energy management systems turning off non-essential equipment). A small amount of deployable electrical storage or a demand reduction strategy can provide more value to the PV system owner and the utility.
At the time, this research concluded that when extrapolating solar load control utility-wide, 104 MW of direct load control provided a firm 249 MW peak reduction from PV (see Figure 1 below). In collaboration with Tom Hoff of Clean Power Research, Dr. Perez has also shown that intermittency of less than 15 minutes can be minimized with a portfolio of PV systems dispersed geographically within a 10 km X 10 km area.
Figure 1: In the ideal situation at left, peak load is reduced by the full installed PV capacity with no disruption from clouds. PV output may be reduced before the end of peak period because of clouds, reducing the achievable demand reduction (middle). By shedding load in response to the reduced PV output due to clouds, the solar load control restores the full demand reduction (right).
The CEC PIER funded two PV demand reduction research and development projects during the same time period as the studies on load control. One project developed the ability for an inverter to dispatch stored electrical energy in batteries upon a signal. The other project deployed a two-axis PV tracker system to supply power directly to irrigation pumps — upon a signal the pumps would be turned off, thus sending all PV electricity as peak electrical production to the utility if necessary. These projects had challenges regarding the signal, the security of the signal and who owned the signal.
Ten years later, this CEC PIER PV research and development work is proving to be quite valuable to address intermittency concerns for large penetration of PV technologies at the utility level. Lower costs for electrical storage technologies due to increased interest in hybrid and electric vehicles are driving the cost-effective economics of PV with electrical storage.
Utilities are investigating various strategies to levelize the electrical production from PV and wind including smart grid, energy storage, microgrids and more. The following is a resource glossary to help the reader navigate the confusing nomenclature of energy storage: Direct Load Control (DLC), Demand Response (DR), Demand Side Management (DSM), Distributed Energy Storage System (DESS), Dynamic Demand Control (DDC), Grid to Vehicle (G2V), Vehicle to Grid (V2G), Variable Energy Resources (VER), Critical Peak Pricing (CPP), Critical Peak-time Rebate (CPR), Advanced Metering Infrastructure (AMI), Real-time Pricing (RTP), Time of Use (TOU), and Day Ahead Demand Response Program (DADRP).
Today’s Storage Costs
At Intersolar 2012 SMUD reported that certain storage technology appears to be below the $400/kWh threshold for cost-effective utility storage. Driven by plug-in hybrid and electric vehicles (PHEV), future stationary applications, like lithium-ion storage, promise to be under $400 per kilowatt hour ($/kWh) including balance of plant costs for power electronics and utility interconnection.
Different energy storage technologies and their current costs broken out by system size have been presented by the Electric Power Research Institute (EPRI) and are shown in Figure 2. Figure 2 shows the installed capacity costs in dollars per kilowatt ($/kW). The difference between $/kW and $/kWh includes the amount of time the storage is used over the system lifetime including all costs. These costs are constantly being lowered, with correspondingly higher and higher values being discovered by the utilities.
Figure 2: Summary of installed energy storage system costs in $/kW by size and type. (Courtesy of EPRI, Source: EPRI 2011 Energy Storage Cost Data Base; EPRI 2012 Energy Storage Cost Benchmarking Report. Estimates are in 2012 dollars and do not reflect regional cost differences across the US. Not all applications and technology options are represented. Site specific and application specific costs can vary significantly.)
Research Driving Storage Costs Even Lower
New federally funded research promises to reduce the levelized cost of electrical storage technology. The Advanced Research Projects Agency-Energy (ARPA-E) recently announced awards for projects that are designed to reduce storage technology costs, including: Ford’s High Precision Life Testing of Automotive and Grid Storage Batteries; ITN Energy System’s Advanced Vanadium Redox Flow Battery, Energy Storage System’s Iron Flow Battery, TVN’s Hydrogen-Bromine Electrical Energy Storage System, Materials & Systems Research’s Advanced Sodium Battery, and a slue of other battery projects including sensor, temperature regulation, energy management and other promising cost-effective solutions.
The Department of Energy (DOE) is also currently funding various smart grid and energy storage solutions for PV projects. On September 1, 2011, the DOE SunShot Initiative announced the selection of eight projects under the Solar Energy Grid Integration Systems – Advanced Concepts (SEGIS-AC) program to receive $25.9 million in total funding. The awardees included:
- Advanced Energy will develop, demonstrate, and commercialize ramp control by using energy storage, islanding detection, and synchrophasor technologies
- Alencon will develop, demonstrate, and commercialize a drastically cost-reduced PV system with a centralized inverter system
- Delphi will develop and demonstrate a modular, cascaded, multilevel PV inverter architecture to lower manufacturing costs
- EPRI will develop, implement, and demonstrate smart-grid ready PV inverters with grid support functionality, utility communication, and control link.
- GE Global Research will demonstrate a systems-level cost reduction approach for the module-embedded PV microinverter
- Satcon will develop and demonstrate a PV inverter control architecture with automatic voltage control capabilities
- SolarBridge will develop an innovative PV alternating current (AC) module that consists of an integrated “universal dock” with high-reliability
- University of Hawaii will develop and demonstrate utility-controlled, smart grid-enabled residential PV inverters at two widely different utilities.
Why Now
Cost-effective PV systems began in space in the late 1950’s, which were used in remote off-grid systems and by the telecommunications industry. When net metering arrived in the late 1990’s, large amounts of PV became grid-tied. Some grid-tied systems included battery back ups in the late 1990’s to early 2000’s, partially due to confusion regarding reliability of the grid and PV. Since then, most grid-tied PV does not include battery back up except for survivalist or critical load concerns.
Utility interest for increased capacity from PV, and the corresponding interest in electrical storage, is being driven by intermittency, green house gas (GHG) regulations, sustainable energy goals, planning for PHEV customers, renewable energy portfolio standard (RPS) compliance, distribution system capacity, and utility peak load management concerns. Increased utility scale capacity from both wind and solar come with technology specific challenges that are also driving interest in electrical storage including:
In the wind sector, many analysts have concerns about the reliability of forecasting, concerns about ramp rates, off-peak production times, and have a perception about unpredictable production during peak demand periods.
In solar, analysts believe that it has a peak period that is generally 4 to 5 hours before the utility peak period, and also have concerns about ramp rates.
The Sacramento Municipal Utility District (SMUD) is now researching PV storage technology with pilot projects. At Intersolar 2012 SMUD reported that on top of their existing generating capacity of 3,300 MW, they are interested in 500 to 800 new MW of PV in the next five years. At these large capacity levels, it will not be acceptable for clouds to minimize energy production, therefore SMUD is moving forward with pilot projects including residential PV and electrical storage, utility sited PV with storage, a residential energy smart community project, solar EV charge port with storage, and a microgrid with energy storage demonstration project. (REWorld has previously written about SMUD energy storage activities here: “Utility Works to Unlock Smart-Grid Potential of Solar-Storage.")
In addition to the utility factors driving the need for storage, new applications and benefits of storage have been identified and investigated including central storage, distributed storage and location specific storage. Some of the benefits from these various applications are listed in Figure 3 provided by Jim Eyer of Strategen Consulting.
Figure 3: Various benefits of storage by sector. Courtesy of Jim Eyer of Strategen Consulting.
The value of storage in comparison to the cost of storage at $400/kWh are reflected in Figure 4 below. Transmission distribution deferral and aggregation values are clearly already above the $400/kWh threshold. When adding up all these values, storage combined with PV is now providing economic incentives to the utility.
Figure 4: Values of storage per application, courtesy of SMUD, July 9th 2012 Intersolar presentation by Mark Rawson, originally attributable to EPRI.
As the cost of PV continues to fall, it increasingly is becoming a generating resource to utilities. Electrical storage has been proven cost effective in hybrid electric vehicles, off-grid PV systems, and is now being investigated in utilities that have large portfolios of wind and solar technologies.
Cost-effective electrical storage technologies driven by research and development is increasing the value and market for PV across the nation. These storage approaches are expanding the grid-tied market and address utility concerns that include intermittency, capacity and other policy-driven goals. Researchers should now investigate the value of retrofitting storage on PV systems, if utilities can benefit and if PV inverter companies can include dispatchable electrical storage options in future products. If trends continue, we will be seeing lots of PV combined with electrical storage in the near future.
Please comment below and help influence the next part of this two-part article. Part II will address a new PV business model which promises to capitalize on electrical storage, utility values and smart grid technologies. Thanks in advance, hope this helps.
We stand on the shoulders of giants who come before us in these efforts; thanks for all the help developing this article including the work of Dr. Richard Perez, Jim Eyer, Mark Rawson, Dan Rastler, SMUD, the CEC, EPRI and many others.
More Articles...
- Solar Power Day and Night: New Storage Systems Control Fluctuation of Renewable Energies
- ARPA-E Announces $43 Million for Transformational Energy Storage Projects to Advance Electric Vehicle and Grid Technologies
- Energy Department Investments to Advance Hydrogen Infrastructure
- Storage, Not Generation, is the Challenge to Renewable Energy
- Utility Works to Unlock Smart-Grid Solar-Storage