Battery Energy Storage Systems (BESS) for Solar PV


The future of Renewable Energy (RE) involves the challenge of stabilising the energy output of green energy sources. Everyone in the energy sector knows this, but what’s the most efficient way of achieving this stabilisation? The ENcome BESS Team gets to the bottom of this question and gives us an overview of BESS for the PV industry.

The Problem: Intermittent sources produce when the energy source is available instead of when the energy is required.

Putting this in context, the peak electricity use in Northern Europe is between the hours of 5 pm and 7 pm. In contrast, the most significant generation of RE is at midday.

With more than 2,500GW of RE capacity in operation around the globe, 48% from the intermittent RE sources Solar and Wind (source IRENA 2020), this newly installed capacity has altered significantly how electrical grids are being used since the systems were first designed.

Conventionally, electricity flows from large power plants to users, however, RE plants have put this model on its head. RE plants are usually installed where there is a big resource or on accessible areas. The plants are connected to local electrical grids rather than wider spreading transmission grids. This causes some issues with outdated equipment in the grid that have been installed to transfer electricity from the large transmission system to the local areas, now being used in reverse.

So how to generate the electricity most efficiently while also using it where and when it is required?

The Solution: Store the electricity locally until it is required.

There are many different ways, historical and new, to store electricity and energy. In the past, pumped hydro and pressured air have been used, but these are reliant on geography, large infrastructure, and not conducive to the message of distributed RE.

Being able to store close to the energy source is more efficient, as there are fewer losses in the system during transfer. In addition, installing a storage device on or near the RE site means that the storage device can be matched to the size of the RE, so no production is lost due to limited storage capacity.

Considering this, an older technology has been identified and is being used in a new, innovative way: Batteries, in multiple forms, are being utilised for this function.

Why batteries? The versatility of battery technology make them a perfect pair for RE.

This technology has many forms, from the tried and tested Lead-Acid, the newer fast-draining Lithium-Ion and the more environmentally-friendly sourced Vanadium-REDOX; these batteries can be sized to the plant, so they can be used as a partner equally for a 4kWp solar PV home installation through to a 316MWe wind plant in the middle of the Australian wilderness.

Batteries with RE pairings have been used successfully to replace highly polluting energy systems, such as grid backup diesel generators in Ireland (EIRE and NI) and on factories with internal backup energy supplies. They have also been partnered with diesel generators and RE devices in remote areas such as sub-Saharan Africa, Caribbean Islands, and Rainforest Communities in a microgrid formation, the largest of which is located in the Australian desert.

Batteries not only have the function of storing energy, but they have also been used to help stabilise the grid for more delicate grid systems and areas of high industry. They can inject frequency into the grid, alter the power factor and reduce fluctuations influenced by mechanical machines, including wind turbines and industrial equipment, generators and users of electricity.

BESS and the World of Solar PV: The O&M of BESS is slightly different from the one of solar PV, due to the fact that they are based on different technologies. Still the O&M processes of both technologies are almost congruent and therefore can be efficiently combined.

From the grid point of view, the BESS plant will have a different function to the RE plant it is connected to. Usually, the BESS is classed as a primary generator, potentially backing up the grid at times of low energy and balancing the grid when there are frequency and power factor fluctuations. This must be accomplished within seconds of the instruction from the grid operator, subject to grid connection agreements.

Alarms, monitoring and reporting, are conducted at a high frequency to keep an eye on the reactivity from instructions from the grid, the balancing of the entire system and the hazardous chemicals that could start a potential ‘runaway’ chemical reaction causing significant health and safety issues for any attending engineers and the system itself.

ENcome and BESS: As an independent service provider for solar PV, O&M is our daily business. ENcome Engineering already has broad experience designing hybrid plants for projects in Europe and Australia. The Engineering team is well versed in designing hybrid plants of multiple sizes in diverse locations found in various countries worldwide.

“BESS is an effective tool to address the need for storage solutions, in particular, since it is a technology complementary to solar energy as well as complementary from an operational perspective” says Sebastian Nieding, Head of Technical Operations of ENcome Group.

ENcome Energy Performance has more than 1.5GW of solar PV energy in its care in 18 countries across Europe and Australasia, some expanding to add BESS. With engineers present in all countries ENcome operates versed in maintenance of BESS plants, solar asset  managers experienced in hybrid and multi energy plants and a 24/7 Competence Center Monitoring, ENcome is a reliant partner not only for Solar O&M but also for BESS O&M.

BESS have not only electrical components but hazardous chemicals and stabilised environments to consider also. The maintenance of the component parts has to be considered carefully due to dangerous substances being present, DC close to AC electrical components and proximity of HV electricity, all of which operate differently to solar PV. Temperature and humidity sensitive equipment, plus the balancing of the battery equipment by the local SCADA systems, also needs to be monitored and maintained accordingly.

Particular nuances of the BESS world are already catered for within the ENcome team. Our H&S specialist and trained engineering staff will always adhere to the most strict of standards, adherence to the COSHH reglations in the UK, in addition to the electrical safety regulations that are in place for generating assets and any access restrictions (such as working at heights).

The ENcome Competence Center Monitoring plays a big part in the day to day O&M of BESS units as regulations vary per country for reaction times to orders from the Grid Operators, however these reactions have to be monitored. One second over the reaction time limit can have serious implications for the grid and all those who are connected to it. The Competence Center Monitoring has the experience of monitoring such strict restrictions with variations on country policy and processes on how to handle incidents that occur on site.

Solar Asset Managers and technicians trained in multi-energy plants are available for consultation, monitoring or full operation and maintenance activities. Please contact us for more information and to be put in contact with the Lead BESS engineer in your region.

Written by the ENcome BESS Team

About ENcome:
The ENcome Group is a leading independent service provider for the technical operation of photovoltaic power plants and the offering of respective engineering and advisory services. In managing and planning the power plants entrusted, the service of the ENcome Group focuses on maximizing short-term availability, production performance as well as long-term value.