Solar power storage: use solar power flexibly

Photovoltaic systems should be installed on every modern roof. Add a solar storage unit and you can realise the full potential of your solar modules.

What are solar power storage units?

A solar power storage unit is normally a battery, an accumulator. Whenever your PV system generates excess solar electricity, you store the electricity in this battery. You can now use the electricity when you need it instead of having to feed it into the public grid as before. This will reduce the annual amount of electricity you have to purchase. A solar power storage unit can thus provide substantial savings as the purchase of electricity is always more expensive than the feed-in tariff.

The capacity of these solar batteries is now sufficient to enable a power storage unit to supply your house with electricity for several hours. The efficiency of solar power storage units continues to increase. Solar power storage units in residential buildings will play a key role in the future energy system where small, decentralised power generation units will dominate.

Benefits of solar power storage units

The significant benefit of installing a solar energy storage system is that you will become independent. Independent from the weather and power suppliers. At a glance:

• Efficient use of solar energy
• Independence from traditional power suppliers
• Reduction of electricity bill by increased self-consumption
• Unaffected by future electricity price increases
• Use solar energy independent from the time of day and weather conditions

Can existing PV systems be retrofitted with a power storage unit?

In Germany more than 1.7m photovoltaic systems with a combined capacity of 49.5 GW had been installed as of 2019. The bulk of these systems do not have a solar power storage unit, which is not a problem as the majority of these systems can be equipped with one. 

There are two types of storage systems: AC-coupled and DC-coupled systems. The terms AC and DC denote Alternating Current and Direct Current. AC-coupled systems are best suited to retrofit existing PV installations. They feature a so-called bidirectional battery inverter, The inverter stores the energy generated by your PV system in the solar power storage unit. The generated electricity can now be used for self-consumption. 

What about the new installation of PV systems?

If you want to acquire and install a photovoltaic system, DC-coupled solar power storage systems are recommended. A battery inverter converts the direct current into alternating current or stores it in the battery temporarily. The inverter also controls the charge and discharge of the battery storage unit and household consumption. The generated excess electricity is fed into the grid. If you are looking to use solar power for your own needs deploying a DC-coupled solar power storage system from RCT Power is a very efficient solution. In standby mode, the electronics of the RCT Power storage system consume just 6 watts. 

Good to know: In the Energy Storage Inspection 2020 conducted by HTW Berlin the RCT Power Storage DC 6.0 in combination with the RCT Power Battery 11.5 kWh achieved best in class results for efficiency in the 5 kW category.

How to determine if a solar power storage unit is worthwhile

With a solar power storage unit, you can increase your self-consumption rate of the electricity generated by your PV system from 25 per cent to 75 per cent. At the same time, you will make savings due to the reduced amount of electricity you by from energy supplier. With a comparative calculation, you can establish the payback period of your investment in the solar power storage unit based on the projected electricity cost savings.

• How much electricity do I consume on average per year?
• How much is my annual electricity bill?
• How much do I expect to pay over the next 25 years?
• Are you planning to add large electricity consumers in the future?

Which battery technology is recommended?

Accumulator technology is constantly evolving. The era of solar energy storage units that where using lead-acid batteries is in the distant past. Lithium-based batteries have established a leading position for these applications. RCT Power solar power storage units use LiFePO4 batteries. LiFePO4 stands for lithium iron phosphate or LFP. The cell chemistry of this battery type belongs to the group of lithium-ion batteries. LFP batteries have a lower energy density and are therefore slightly larger than other batteries. The bigger size is for stationary storage units not really of importance.  The lower energy density helps to avoid thermal runaway and subsequent fire when cells suffer from mechanical damage that can result in internal short circuits. LFP batteries are much safer  than other Li-based batteries

However, the battery technology used by RCT Power and the dedicated battery management system developed together with the KIT (Karlsruhe Institute of Technology) provides you with even more advantages. The finetuned combination of battery technology and battery management system results in high cycle stability, ensuring a very long service life, even under high load. Benefits at a glance:

• Very safe, no risk of fire
• Very high number of charging cycles, resulting in longer service life
• Depth of Discharge exceeding 90% for maximum storage utilisation
• High efficiency exceeding 90%.
• Warranty on the solar power storage unit: 10 years

Back-up power for security of supply

Solar power storage units are very safe. The RCT Power Switch adds the security of supply to your PV system and increases your independence level from the power grid. In the event of a power failure, important electrical appliances such as refrigerators or WLAN routers continue to be supplied with power. As soon as the mains power fails, the RCT Power Switch automatically disconnects from the mains supply, and the storage battery takes over to supply power in your house. You will always have back-up power available.

Having a solar power storage unit with a back-up power functionality is a sensible option for your system, especially considering the increased number of newly established ‚Home Offices‘. Even in the event of a power failure, you can continue to work from home. The reaction time in the event of a power failure is only 5 to 10 seconds. To optimise the security of supply, the device ships with two outputs: one for power consumers that absolutely must be supplied with back-up power and one for those devices that are not essential in an emergency.Benefits of solar power storage units with back-up power:

• The functionality of the PV system is maintained
• Continued recharging of the storage battery by the PV system
• Ideal home office support – avoids WLAN router outages
• No cooling appliances outages
• No illumination outages

Solar power storage at a glance

Solar power storage units are getting increasingly more efficient and cheaper to buy. You can either utilise them to retrofit your existing solar systems or include them when you plan a new PV system installation. LiFePO4 batteries are very safe and have a long service life and are therefore recommended as the battery technology to use in solar power storage units. A useful addition to the storage unit is the RCT Power Switch to enable a back-up power supply. With an RCT Power storage unit, you will always be on the bright side.

Please feel free to contact us if you have any questions.