One of the pioneers of using aggregated residential energy storage systems to create virtual power plants (VPPs), Sunverge has been active in the market since 2011 and Martin Milani became chief executive officer (CEO) in late 2017, taking over from company founder Ken Munson. The company has done projects in geographies including Canada, Australia and Japan, but is presently most-focused on its home market in the US. Here’s some of the backstory and where the company is going these days, as told to Andy Colthorpe.

The term VPP is old. It comes from energy efficiency and demand response and in energy storage the ability to connect or curtail loads. For example, reducing load by half a megawatt would be like having a half a megawatt power plant, hence the term virtual power plant.

Sunverge had a slightly different point of view. Curtailment was obviously one thing but the ability to actually use energy storage in conjunction with solar, to pump energy back into the grid to do things like volt/VAR optimisation, reactive power support, frequency response and frequency regulation. From very early on, Sunverge also saw those things which aren’t virtual at all – they’re actually very real.

The beauty of distributed storage controlled and aggregated by a multi-service platform is that there are many different ways to monetise the services at any given time on both sides of the meter.

In the US you have the concept of nodal pricing and locational marginal pricing, so electricity has a certain value, a certain price, at a certain location, at a certain time – that’s why energy storage can be extremely effective in addressing those kinds of needs as well.

I think a lot of people thought this market was going to move a lot quicker back in 2014 and 2015 than it really did. That’s been a challenge for Sunverge and a challenge for everyone else. In many ways, Sunverge has been able to weather that a little bit better than some of the others because [as well as the solar-focused market] we also focused on the vertically integrated utility and in fact we’ve had utility programmes where they are actually applying energy storage not just for Demand Side, but also to address a grid condition like distribution asset upgrade deferral to deal with feeder load situations, to deal with capacity [issues] and over-penetration of solar.

Our publisher, Solar Media is currently hosting a season of online conferences, the Digital Series. Topics still to run include Solar & Storage Finance (1-5 June) and Energy Technologies (15-19 June), while last week we saw the Large-Scale Solar series. Our Energy Storage Digital Summit got us off to a low carbon yet globe-spanning start and took place from 11-15 May. From a full week of webinars and panel discussions, there was a huge amount of ground covered. Here are some more of our takeaways and there are links below to some of the news and views we’ve already posted. ​

1. Developing energy storage projects in the age of COVID-19 amplifies existing challenges
   Erik Stokes, branch chief at the California Energy Commission hosted a panel discussion: “Timeline to building a safe storage project” on the first day. Speaking to three senior team members at developers Soltage and Hecate Energy, and from consultancy Geostrategies, Stokes heard that COVID-19 is unsurprisingly having an impact on project execution.

Brian Schmidly, founder at Geostrategies said that most battery and equipment manufacturers sending products out from Asia are now back online, but that there are likely to be delays and bottlenecks toward the end of this year as everyone plays catch-up. This is perhaps similar to the early days of solar, Schmidly said, when demand outstripped available supply for PV modules.

Hecate Energy general counsel Holly Christie noted that while in the first few weeks of the pandemic, many parties claimed force majeure clauses, since force majeure refers to something unforeseen, after a period, it becomes more difficult to argue that the delays are “now not unforeseen”. Change of law provisions are now “fluid notions that were not necessarily so before”.

Dirk van Ouwerkerk, senior VP of energy storage development at Soltage, said that the pandemic’s effects on supply chains need to be monitored very, very closely, and that there are two types of supply chain issues: “materials getting through to manufacturing, and then getting manufacturing product to the projects”. This includes the “vast majority” of manufacturing for both LFP and NMC battery cells, which is in China.

Van Ouwerkerk said that the delays are not structural in nature. He expected to see three to six months of delays but felt that the delays are “decreasing and probably not there next year”. On a related note, he went on to say that with energy storage still at a relatively early stage of industry maturity, there hasn’t been the same level of standardisation as achieved in solar. Every project is still very different and the cost of capital high. Soltage develops projects, van Ouwerkerk said, there is a constant reassessment of “fatal flaw” analysis.

Used electric vehicle (EV) batteries can be repurposed to store electricity generated by large scale solar plants, according to an MIT study.

The U.S.-based researchers claimed even devices which have lost 80% of their original capacity could offer a better investment prospect for solar-plus-storage projects in California than purpose-built, utility scale batteries, not least because such ‘second life’ EV batteries could cost as little as 60% of their purchase price.

MIT research co-author Ian Mathews conceded technical hurdles remained to the deployment of used EV batteries on a large scale, such as aggregating batteries from different manufacturers and screening which devices could be reused. However, Mathews insisted used EV batteries still offered a persuasive enough business case to justify the cost of recovering them, screening performance and redeploying them.

Optimal operation

The researchers used a semi-empirical model – including some ‘pre-cooked’ calculations – to estimate battery degradation, and concluded operating such aggregated storage devices at 15-65% of full charge would extend their second life. “This finding challenges some earlier assumptions that running the batteries at maximum capacity initially would provide the most value,” the scientists stated.

Mathews said the feasibility of second-life EV battery storage would depend on the regulatory and rate-setting regimes under which they would operate. “For example, some local rules allow the cost of storage systems to be included in the overall cost of a new renewable energy supply, for rate-setting purposes, and others do not,” he said.

Algorithms

The academic added, longer-term pilot studies are needed to assess the potential of such systems.

The MIT researcher noted control algorithms may be adapted during projects to lengthen the feasible lifetime of such facilities. “We think this could be a great application for machine-learning methods,” said Mathews, “trying to figure out the kind of intelligent methods and predictive analytics that adjust those control policies over the life of the project.”

The successful reuse of electric vehicle batteries for grid scale storage would also require buy-in from EV manufacturers, energy storage businesses, solar project developers and power electronics specialists, added Mathews.

Sweden-based storage system provider Northvolt has developed a new lithium-ion battery based on a modular approach that makes it suitable for a range of different energy market segments.

The manufacturer said the new Voltpack Mobile System is an ideal solution for remote or weak grids and EV charging. However, it has claimed that it can also be used for balancing, grid flexibility, and ancillary services.

“Voltpack Mobile System delivers up to 250 kW with a scalable capacity from 245 to 1225 kWh of available energy,” Northvolt said. “The system scales through a central interface hub, which can connect in parallel up to five self-contained Voltpacks, each containing three liquid-cooled, industrial-grade battery Voltpack Cores.”

Voltpack Mobile Systems can be connected in series if more storage capacity is needed, with the central hub serving as an interface for applications such as home inverters and auxiliary systems. The battery technology, as well as the inverter systems and battery management system, were designed and manufactured by Northvolt.

Vattenfall

Utility Vattenfall is testing the system at its facility in Alvkarleby, Sweden. “Vattenfall will be the first to offer the battery unit to the market, and have identified the need for sustainable solutions at industries, for microgrids, construction sites as well as for event organizers,” Northvolt said.

Torbjorn Johansson, head of Vattenfall Network Solutions Sweden, said that the company will offer the battery storage solution as part of its “power-as-a-service” concept. “(This) means that we deliver a complete package with ownership of the energy storage and manage it to the specification of the customer,” he added.

Drammen Eiendom KF – a company owned by the municipality of Drammen, Norway – has developed a project to store solar energy as heat. The system can store energy provided by 150 m2 of solar thermal collectors and 1,000 m2 of PV panels in 100 boreholes in granitic gneiss rock, each with a depth of approximately 50 meters.

“GeoTermos is expected to return around 350,000 kWh/year in the form of heat at various temperature levels during the heating season,” said Randi Kalskin Ramstad, a shallow geothermal energy and hydrogeology specialist at the Norwegian University of Science and Technology (NTNU) and engineering services provider Asplan Viak.

The electricity provided by the PV installation produces heat by using air as a heat source for the CO2 heat pump. The heat is then stored in the boreholes during the spring, summer and fall. In the winter, it is used for low-temperature heating in a number of nearby school buildings.

“The system performance of the energy system is quite high,” Kalskin Ramstad told pv magazine. “The operation of the plant has now just started, with heat charging of the boreholes.”

Water is used as a collector fluid in the boreholes, which provides several advantages compared to glycol-based collector liquid, including lower viscosity, better thermal properties, and lower costs. It is also environmentally friendly.

The GeoTermos system – with energy storage, a heat pump, and an accumulation tank – is able to provide approximately 300 kW of heat power for short periods during peak load, and is regulated by the temperature levels and heat power demands.

PV system

The 200 kW PV installation, which was built by local installer Solar Technology Scandinavia SAS, was deployed across four different rooftops at a school. The NOK 3 million ($299,000) system relies on 616 Panasonic VBHN 325 SJ47 PV modules and SolarEdge three-phase SE25K inverters.

The UK government has confirmed changes to the Capacity Market which are designed to remove barriers for demand side response (DSR) and energy storage, making it easier for clean technologies to compete in auctions.

The changes include reducing the Minimum Capacity Threshold from 2MW to 1MW. DSR will now be able to apply to prequalify to bid for all the agreement lengths in the capacity market, provided they can demonstrate the relevant CAPEX threshold.

It will now provide legislative underpinning for the long-standing 50% set-aside commitment for T1 auctions, along with methodology for working out the minimum amount of set-aside. T1 auctions are set up to guarantee capacity is available to the system to keep Britain’s lights on the following winter, whereas the other type, T4 auctions, look to secure adequate capacity four years ahead.

A formal, annual review of new capacity technologies that are not currently competing in the Capacity Market but which could help to provide security will be brought in.

Reporting and verification for the introduction of CO2 emission limits will also be brought in, with emissions limits set to apply to capacity which existed before 4 July 2019 from 1 October 2024. Britain’s European neighbour France recently introduced its first ever Capacity Market auction with a low emissions requirement, awarding contracts to more than 250MW of energy storage assets as a consequence.

Changes help clear the path forwards for clean technologies, association chief says
“A common barrier to advancing the UK’s energy storage sector is that our electricity grids and major energy policies from government are set up for an age of large-scale, centralised fossil power stations,” explained Dr Nina Skorupska CBE, chief executive of the UK’s national Renewable Energy Association (REA).