Battery Storage Systems

Please note: This article is for educational purposes only. Always consult a qualified energy storage installer before making any decisions about battery systems for your building.

Battery storage systems offer commercial buildings three core benefits: reducing peak electricity costs, maximising solar PV self-consumption, and providing backup power. Understanding how battery storage works and how to size it correctly is key to assessing whether it makes financial sense for your organisation.

Contents

1. Three Main Purposes of Battery Storage
   1. Reducing Peak Electricity Costs
   2. Maximising Solar PV Generation
   3. Back-Up Power
2. Assessing Financial Benefits
3. Battery Sizing and Capacity
4. Modes of Operation with Solar PV
5. Safety and Maintenance

Three Main Purposes of Battery Storage

1. Reducing Peak Electricity Costs

Some businesses face expensive peak rate electricity tariffs and additional charges from suppliers for drawing large quantities of power from the grid at certain times. Battery storage systems allow charging during off-peak hours when electricity is cheaper, then using stored electricity during high-cost periods. This is known as load shifting and can significantly reduce energy bills for businesses with variable consumption patterns.

2. Maximising Utilisation of Surplus Solar PV Generation

Buildings with solar PV systems sometimes generate more electricity than they consume, with surplus generation exported to the grid. Installing a battery allows that surplus to be stored and used within the building instead, reducing the need to purchase electricity from the grid. This increases self-consumption of solar PV-generated electricity, reducing reliance on grid power and potentially delivering further cost savings.

3. Back-Up Power

Batteries provide backup power in certain scenarios, particularly in large commercial buildings using centralised lead acid battery systems for emergency lighting. For buildings requiring high reliability with heavy loads, diesel generators are generally preferred over batteries due to their greater power output capacity.

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Assessing Financial Benefits

To assess the potential financial benefits of a battery system, a thorough understanding of electricity consumption is essential. Analysing half-hourly consumption data across a full year reveals consumption patterns and helps identify surplus electricity available for storage, particularly in relation to solar PV generation.

Financial models depend heavily on system sizing and require a comprehensive assessment. Consultants use modelling algorithms to analyse building energy consumption and solar PV generation profiles, factoring in time-of-day import and export tariffs to determine the optimal battery storage capacity for maximising financial benefits.

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Battery Sizing and Capacity

Battery systems have limited capacity to supply power compared to the grid. In instances of high peak loads, such as heavy machinery, a battery system may not suffice and grid power will still be required. Battery capacity is typically measured in kWh for storage (e.g., 400kWh, or 0.4MWh) and in kW or kVA for power output. Some manufacturers specify size by power rating and discharge duration, enabling modular configuration for varying building needs.

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Modes of Operation with Solar PV

When combined with solar PV, battery energy storage systems typically operate in three modes:

1. Charging from solar PV — used when there is a surplus of solar energy being generated.
2. Charging from the grid — used when grid electricity is cheap, typically during off-peak hours.
3. Supplying power directly from the battery — used when grid electricity is expensive, such as during peak tariff periods.

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Safety and Maintenance

• Modern lithium-based batteries require proper installation, commissioning, and regular monitoring for safety and efficiency.
• They include sophisticated Battery Management Systems (BMS) to prevent overheating and over-discharging.
• Lithium battery fires are difficult to extinguish, so fire risk assessments are essential before installation.
• Batteries are often placed outside buildings or in lower-risk areas. In high-risk locations such as car parks or loading bays, additional security measures should be implemented.

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