Many construction professionals across various disciplines and areas of expertise are sure to have heard an increase in the use of the acronym ‘BESS’, which is a simple moniker for Battery Energy Storage Systems. Whilst battery technology isn’t new, realising batteries for domestic, commercial and even grid level energy storage is becoming a much more feasible concept for dealing with carbon emissions. This follows a rapid improvement in battery efficiency, cycles of operation, safety, spatial footprint and uptake over the last 5 years.
Why now?
Our society urgently needs to act on climate change by reducing greenhouse gas emissions. To assist this, we need to make electricity our primary form of energy and progressively decarbonise the electrical supply grid; effectively replacing fossil fuel generators (coal and natural gas) with renewable sources such as wind, solar and tidal energy. In tandem, we must also decarbonise our end-use energy by shifting to electrified solutions; think electric vehicles and heat pumps. Nuclear energy could have made an important contribution to this decarbonisation, but historic strategy decisions by the UK government, several high-profile disasters and general negative social rhetoric around the issue has seen nuclear become somewhat of a pariah.
Government targets for electrification are now incentivised by more stringent building energy and thermal compliance requirements set out in the building regulations of each jurisdiction.
In Northern Ireland, recent updates to Technical Booklets F1/F2 (2022) leave us approximately one step in building regulation updates behind England and Wales in terms of compliance. In practical terms, oil and gas are heavily penalised in these assessments, while air source heat pumps are not. In addition, zero carbon sources (particularly solar) can be used as an offset to improve the compliance where shortfalls are present in the fabric or other systems. This is being determined and communicated to domestic and commercial clients through SAP and SBEM tools respectively.
The renewable problem
Zero-carbon or renewable energy sources come in various flavours (think geothermal, hydro-electric, tidal energy), but only two sources have potential to be installed in most locations at both micro and macro generation scale: solar and wind. Both sources have the potential to revolutionise our future and that of our children, but they have a common inherent problem; weather dependence. Solar requires high levels of solar irradiation which are not available during cloudy weather or darkness, while wind blows on a completely unpredictable intermittent basis. In short, if we cannot store the energy from these sources to offset their intermittent nature, they are not a viable replacement for fossil fuels (which are entirely demand based and can be switched on and off at will).
The solution
Evidently energy storage is the answer and BESS is the largest growing method of energy storage. At a domestic level, solar PV makes little sense without a battery in tandem as demand is generally at its highest when the sun is absent. Wind is so irregular the only benefit to a domestic user is to export which, in the absence of historic and lucrative Renewable Obligation Certificates (ROCs), could generate as little as £0.09/kwh for the prosumer, while current rates of import are approaching £0.40/kwh. Clearly exporting for profit is not what end users should be targeting.
Instead, a battery system sized and designed by a competent electrical engineer can allow surplus energy to be stored when the system is over-generating and then utilised when required by automatic discharge of the battery. This is kind to the environment and makes strong commercial sense. A correctly designed and controlled system should consume every single kWh of electricity generated, limiting export to surplus power generated during excessively sunny spells and paying for itself in 7 – 10 years in most cases, perhaps sooner. This exported power is then available for use by other customers and the prosumer (a new term from The Institution of Engineering and Technology for a domestic producer and consumer) is paid for each kWh of export. It is important to note however that the electricity network is not set up for distributed generation in Northern Ireland, so where the utility is unable to sustain the export due to network issues, zero export arrangements may be put in place by the Distribution Network Operators.
BESS also offer a further opportunity for consumers, particularly on a commercial level. Dual tariffs are readily available for consumers and coupled with BESS allow consumers to avail of charging BESS systems at night-time tariffs rates saving 40-50% compared to peak day-time rates.
The bigger picture
At a commercial and industrial level, wind will usually benefit from a battery in tandem as it is fairly certain power will be generated at night when demand is low. Solar PV on the other hand may in some cases simply bite a small proportion out of the user’s overall import during the day, never over-supply and therefore a battery storage system should never be recommended. In other cases, solar PV may be employed at large scale on its own, or with Combined Heat and Power units CHP, wind turbines and other sources all on the same site (think large college campus or industrial facility) and a battery will become an integral part of maximising the capture of ‘free’ energy and limiting the need to import expensive (and not yet fully decarbonised) grid power.
Sophisticated solar PV inverters and battery controllers can provide extremely close control of systems meaning that the flow of energy to and from the battery (and to and from the site to the grid) can be managed with precision. This ensures energy capture is maximised, but also that export control agreements can be complied with if present, generally by disconnecting generation rapidly on detection of over-generation in a battery full state.
To complete the picture, private industry is central to the deployment of so-called ‘grid-scale’ battery storage connected to the grid at transmission voltages (33kV and 110kV). These systems store enormous amounts of energy during the night when demand is low (evidently purchased at a reduced cost), and then discharge during daytime / evening peaks in demand when called upon. These systems will be a necessity to stabilise future supply as a decarbonised electrical grid is inherently ill-equipped to cope with providing steady-state power in changing weather conditions.
Take away
It is imperative that your clients are receiving the most technically sound and up to date advice on renewable generation and battery energy storage systems, from the smallest dwelling to the largest factory. This ensures that the requirements of the building regulations are being met, clients are maximising savings and, more fundamentally, that we are all effectively maximising energy capture to support the wider decarbonisation of our societies.
Bennett Freehill are currently involved in renewable / BESS schemes at domestic level, on industrial schemes and at high voltage grid-scale; are Passivhaus and NZEB (Nearly Zero Energy Buildings) designers and provide simulated building energy modelling services. We are in a unique position to assist our clients with everything from high level strategic energy planning to detailed electrical design of complex BESS systems.
Many thanks to the Royal Society of Ulster Architects (RSUA) who published this article in the RSUA Practice Services Scheme e-Bulletin Issue No 97. 2022.
