July 13, 2021

Challenges and opportunities: The growing demand for BESS integration with PV


This is a guest blog post from Sinexcel. Connect with Sinexcel at #ESACon21 in Phoenix, AZ, December 1-3. 

Global solar PV markets had their biggest year yet in 2020, despite some lost momentum in first half of the year due to COVID-19-related shutdowns and disruptions. 134 GW of solar PV was installed globally in 2020, a 23% increase compared to 2019 and reaching a cumulative installed base of almost 750 GW, according to Global solar PV market outlook update: Q1 2021 from Wood Mackenzie.

With the hot PV market, countries have also introduced policies to restrain and improve the PV market, so that it can develop better. Many countries require PV plants to be equipped with 10% to 20% battery energy storage system (BESS), which has also greatly boosted the development of the energy storage market.

At the beginning of our business, any project with over half a megawatt of battery storage was rare and significant. Five or six years ago, two or three enquiries that exceeded the one megawatt-level will come to our desk each week from all around the world. Some of these might even exceed 10 MW. With the development of renewable energy technology and policy, projects in the tens of megawatts and megawatt-hours are no longer a rarity and the world’s largest operational battery storage systems run into the hundreds of megawatts of power, and even exceed the thousand megawatt-hour marks for energy capacity in some cases.

Undoubtedly, we are at the front gate of a new era. However, we will also be facing more challenges, such as the imbalance between supply and demand of electricity, impact on stability of power grid from numerous installations of renewable energy, the safety of battery systems, long recovery time of system failures, regional power shortages, high initial cost of over-configuration on battery systems, low utilization rate of parallelization of battery strings, and so on.

We have always believed that the modular DC-coupled system is an effective solution when facing the current main problem. And it has more advantages than the AC-coupled solution on efficiency, flexibility, and stability.

In the DC-coupled system, the DCDC converter with Maximum Power Point Tracking (MPPT) offers higher efficiency and lower loss when charging the battery from PV energy, since there is no more twice ACDC conversion. It could also be used with either an existing solar farm to charge the battery by connecting directly to the combination box or a new installation with Battery Energy Storage System to get PV connection. The isolation between DC and AC can also eliminate the impact on the local grid and maximize the value of the renewable energy.

And with the modular design, we believe it will perfectly solve many of the problems we are facing today in behind-the-meter market.

During the design of the BESS, the degradation of battery should be considered to allow enough energy could be used till end of life. So, the initial investment cost will be higher than actual demand. In many projects, the size of the system will be limited to current load size due to the budget and the possibility of future growth is ignored. But the future expansion on AC side has quite a lot of risks on both cost and local approval for grid connection.

By using a modular solution, a project can support the mixture of used and new battery system, and the batteries and PV panels could be added by phases, which offers highest flexibility for the demand and cost for the system during the whole lifetime.

A modular solution is also easier to maintain and troubleshoot independently, without affecting other modules. The failure of a single module does not affect the operation of the whole system, and the impact of failure on the energy storage system is minimized, which can achieve flexible distribution, smooth capacity expansion, suppression of the scope of failure and great reduction of the cost on operation and maintenance.

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