Interest is growing from data center operators, commercial and industrial (C&I) and other organisations in new models for interacting with the grid.
These organisations want to better understand how they can lower energy costs, and monetize existing power infrastructure but without effecting resiliency and service level agreements.
Examples of so-called critical energy (CE) services in action could be a data center operator using excess UPS capacity for distributed energy storage either directly or via an aggregator partner. This is an example of behind the meter (BTM) services but utilities and grid operators are also developing a whole range of front-of-the meter (FTM) services using energy storage at a much larger scale.
Vertiv held a recent webcast to provide context and more detail on this important and emerging area.
Some of the key questions from webcast attendees and the answers from Vertiv experts are outlined below:
Question: How do you ensure there is also enough battery capacity in a BTM deployment to guarantee availability of the load?
Vertiv: We have two ways of preserving that. We have the hard way and the soft way. Our standard UPS (Liebert EXL or Trinergy Cube) are equipped with a parameter within the UPS controller which is accessible only by our service engineers via password protection. That parameter defines the percentage of the battery that is reserved only for back-up purposes. That means that the UPS will only execute on external commands such as exporting energy to the grid or going to battery mode if the battery capacity is above that percentage. This is a hardwired percentage that is not accessible from the outside. The softer way is to delegate this service level to the external controller. We can set that threshold at 0% and have the external control have full control over the service level of the battery. It depends on the preference of the customer.
However, there are some consequences. If the battery capacity reaches the threshold, the uninterruptible power supply will stop delivering any kind of external service so the UPS will not be available to serve external commands. In that case the right-sizing of the battery bank is critical to ensure that you can either fulfil a contract with a grid provider or you have enough battery to serve your internal purposes.
Question: What are the advantages to a customer of using an aggregator for BTM services as opposed to managing contracts directly with transmission system operators?
Vertiv: The main advantages of using an aggregator are for the operation of the system. If the customer wants to deal directly with the national grid operator, the customer must manage and operate the system correctly. So, they must manage and maintain the site controller, so technically it is more challenging. It also requires external consultancy and system designers etc. The other complication is that the customer must manage the contract, participate in tenders some of which need to be renegotiated every six months or even more frequently – perhaps even daily. So for the customer it becomes quite challenging to manage those contracts. The advantage however of a direct relationship is that you enjoy the full revenues.
With an aggregator model, the aggregator sits between the service and the customer. They will of course retain a percentage of the revenues but they will manage the contracts. They will bear the liability and they will operate the system. We are open to both models and are working with aggregators but also with customers with a direct control system. We think both models are viable but there are clear pros and cons for both.
Question: Will the grid see UPS as a source of supply in the same way as Combined Heat and Power (CHP) or Photovoltaics (PV)?
Vertiv: This is a tricky question as for a UPS without grid support functions then the answer is ‘no’ as it is a passive load. As such it does not need to comply with any interface regulation like the G59 in the UK or others across Europe – unfortunately there is no European standard right now. The same goes for a uninterruptible power supply with these functions enabled but with the possibility to inject back into the grid disabled as it will only be able to regulate the input power from load power to zero which is back-up. Only in the case where the customer is prepared to use the positive functions – so feeding energy into the grid – then in that case yes then the UPS must comply with the same regulations as for the PV fields – the regulations for self-energy production.
Question: Why do some energy storage deployments (FTM) use a mix of Lithium Ion and traditional lead-acid batteries?
Vertiv: Some of the early deployments used a mix of batteries because the use of Lithium Ion batteries was still in the test-phase. Lead acid batteries are quite good when it comes to pushing energy into the grid. However, they are less suitable for the ‘negative services’ when you must draw power from the grid in the case of over-frequency. Most new sites for FTM will only use Lithium Ion batteries.
For more on both our BTM and FTM critical energy services head to our insights webpage.
