Anesco was the first to add storage to its solar farms and retain accreditation, prompting Ofgem to prepare guidance to the industry. Image: Anesco.

Ofgem has published guidance outlining how developers and asset owners can add storage to their subsidised solar installations without losing accreditation to the Renewables Obligation (RO) and Feed-in Tariff (FiT).

Three months after first making the ‘game changer’ decision to allow solar developments to retain their accreditation under the RO, the regulator has now set out what it calls ‘non-exhaustive’ guidance, adding that the examples included within the guide are not intended to cover every possible approach to co-locating storage.

This broad approach is due to the fact that the legislation underpinning the RO and FIT schemes do not refer to storage facilities, with co-location of storage neither expressly prohibited nor provided for under the schemes.

“However, we consider that where the requirements of the schemes continue to be met, storage can be deployed and the accreditation of RO generating stations or FIT installations can remain valid under the existing legislative framework,” the guidance document states.

Co-locating storage with RO sites

RO Certificates (ROCs) can be issued for the net renewable generation from an accredited generating station which is supplied to customers in Great Britain or Northern Ireland, or has been used in a permitted way as prescribed in the scheme legislation.

Those with co-located storage will need to demonstrate that they continue to meet these requirements once the storage has been installed in order for ROCs to be issued.

Metering must be set up to allow the operator of the generating station to accurately measure the output as well as any input electricity needed on site. This will need to ensure that electricity from ineligible sources does not augment the meter readings for the station, meaning the net generation from the RO generating station can continue to be accurately measured.

Ofgem deems this to be particularly important if the storage facility can also be charged by other sources of electricity which are not eligible for support under the RO.

Other factors to consider when adding storage include demonstrating that the electricity generated on-site is used in a ‘permitted way’ if not supplied to customers, specifying which of these requirements are being met in order for ROCs to be issued.

Where a co-located storage facility is used to meet on-site demand, the electricity generated and supplied to the storage may also be eligible, while the operator of a project that generates and supplied to a third party facility by a private wire arrangement or similar will also remain eligible under the correct circumstances.  

Co-locating storage with FIT installations

As stated by Ofgem’s head of renewables Luke Hargreaves last month, the FiT scheme offers a more complex path for co-location with storage owing to the fact that the scheme does not permit using multiple meters to measure any electricity imported, to calculate net generation or export.

FIT generation payments are made based on the total generation produced by an installation. A generation meter is normally located close to the point of generation and measures the electricity generated solely by the accredited FIT installation.

For generation payments to continue to be made for an installation, the FiT licensee must be satisfied that the generation meter only measures electricity generated by the FIT installation and not from other sources.

Like the RO, this is particularly important for installations where the storage can also be charged by electricity imported from the grid and is installed before the generation meter.

This can be done in two ways, beginning with the correct configuration of the installation. If the storage facility can only be charged by the FIT installation or the storage facility is installed after the generation meter, then it would be clear that the generation meter only measures generation from the accredited FIT installation.

The second option comes in the form of the generation meter that is used. This must be capable of measuring the electricity generated by the accredited FIT installation only. Payments cannot be made for electricity generated by an ineligible source. However, this measurement must be undertaken by a single meter.

If it is not clear that the generation meter produces a reading of the electricity generated only by the FIT installation, then the generator will not be entitled to receive generation payments.

Those sites where it is not possible or practical for export to be measured via an export meter may receive deemed export payments. These are calculated by multiplying the generation meter reading for the FIT installation, by a percentage – 50% in the case of solar PV.

Where it is possible to be satisfied the generation meter measures only the generation from the accredited FIT installation, deemed export payments can be made. This remains the case for FIT installations with co-located storage

For the metered export requirements, FIT licensees should only make metered export payments against an export meter reading which measures electricity that is generated by an accredited FIT installation and flows onto the grid.

This payment must be calculated with reference to the export meter reading only and cannot be calculated using separate input and output meters to calculated a net output value.

Like with the generation payments, metered export remuneration can be retained via configuration of the installation – if the storage can only be charged by the FIT installation it would be clear that the export meter only measures generation from the accredited installation – and the choice of export meter.

This must be capable of measuring the electricity exported by the accredited FIT installation only however this measurement must be undertaken by a single meter as using multiple meters to calculate the net export is not permitted under the FiT.

Where storage is co-located and it is not possible to identify whether the export meter measures export from the accredited FIT installation or another ineligible source, the generator will not be entitled to export payments.

Neither the RO or FIT legislation provide for a process for generators to obtain prior assurance from Ofgem that intended changes to co-locate storage will not impact a station’s accreditation. Each assessment of system changes will be carried out on a case-by-case basis once the change has been made and notified to Ofgem within two weeks of the alteration occurring.

Generators are advised to seek their own legal and technical advice before making any changes to their generating station or installation, or investment decisions.

Ofgem’s full guidance document comes complete with a number of example diagrams for a number of storage scenarios across both the RO and FiT schemes.