Optimise and store your Photovoltaic energy

Ideally, the electricity produced from the photovoltaic system should be consumed directly.

If the photovoltaic produces a surplus, then the surplus electricity can either be returned to the utility via the grid (mains supply) or the surplus energy can be stored in an in-house photovoltaic storage.

How does a photovoltaic storage work?

Basically, the power storage works like a rechargeable battery, which we use in the home.

Originally mostly lead accumulators were used, which are less and less used due to technical disadvantages (little depth of discharge, temperature sensitivity) and above all because of the toxic ingredients.

Currently, the most prominent solar power storage technology is lithium-ion technology. Known by the e-mobility company TESLA, many photovoltaic storage providers have focused on this technology.

The main advantage in the use of lithium-ion technology as a solar battery lies in the high energy density, so it takes little space for the photovoltaic storage in relation to the storage capacity.

Currently there is a noteworthy and practically established alternative in the market for solar storage.

The saltwater electricity storage technology.

When the saltwater technology is used as a solar storage, then you build on the safest and most environmentally friendly PV storage on the market. The saltwater solar energy storage can neither burn nor explode, consists of natural materials and is maintenance-free.

Technically speaking, all three photovoltaic storage technologies have a similar structure. They consist of anode and cathode and have an electrolyte as carrier material for the ion flow. If the battery is charged or discharged, the ions migrate to the anode or cathode or vice versa.

Cost comparison

When comparing different photovoltaic power storage systems in addition to technical advantages and disadvantages it is important to understand the effective cost of electricity storage. On the one hand, the acquisition costs, which are usually defined in euros per kilowatt-hour (EUR / kWh).

For a real lifetime cost comparison it is best to use as a basis the usable kilowatt hours. Some photovoltaic storage have a lower usable storage capacity, which at first glance may give a distorted picture in terms of comparison of the initial costs. Relevant are the total costs per usable storage capacity in kWh.

Costs of photovoltaic storage system

The right cost comparison for the photovoltaic storage should be based on the cost per kilowatt hour, so how much a kilowatt hour costs from the power storage. The essential parameters in the cost comparison of solar energy storage systems are:

  • Number of cycles (how often can the power storage be charged and discharged)

  • Discharge depth (to what degree can I use or unload the power storage)

  • Efficiency levels of the PV memory (how much of the stored energy can I use)

Generally we speak of energy throughput in kWh, which is calculated as:

Usable storage capacity x Number of cycles x Discharge depth x Efficiency level = usable kilowatt hour in kWh

An Example of cost calculation for photovoltaic storage

We have a photovoltaic storage with 1 kWh of usable storage capacity with 5000 cycles, a discharge depth of 100% and an efficiency level of 90%. That’s 4,500 kilowatt-hours of energy throughput.

The kilowatt hours of energy throughput are then compared in the cost comparison to the cost per kWh.

If the initial costs are 800, – Euro per kWh, then the effective cost per kWh is 0.17 Euro.

It is important to compare the solar storage properly. For practical use with a photovoltaic system you need in addition to the battery, an inverter and an energy management. Thus, the costs should be compared holistically and not just the storage only.

GREENROCK saltwater battery

Is a photovoltaic storage system economical?

In order to answer this question, you need two more information in addition to the effective costs per kWh of the solar energy storage (see calculation above).

1. Current electricity costs per kWh (How much is the purchase from the grid.)

2. Feed-in remuneration per kWh (How much will I get back if I feed my photovoltaic power into the grid.)

In this way, the economic efficiency is mathematically answered fast and easy. A photovoltaic power storage is economically useful if the current purchase costs less the feed-in tariff received are higher than the effective cost of the photovoltaic electricity storage.

If the current electricity purchase costs (excluding sales tax) are 22 euro cents per kWh and you get a feed-in tariff of 2 euro cents per kWh, then you save with a power storage 3 euro cents per kWh, taking the above costs as an example used.

Of course, it should be noted that PV storage is seen as an investment in the future. Historically, effective electricity costs have increased in recent years. Thus, the electricity storage is also an insurance against further increases of electric power prices.

In addition to the pure economic calculation of the solar power storage the system offers further benefits. If the PV storage is equipped with emergency power capability important consumers (e.g., alarm equipment) can operate even in the event of a power outage. Safety and reliability of key electrical consumers is ensured.

A standard application of a photovoltaic storage system

Energy-flow throughout the day

To calculate the size of a photovoltaic storage system for private homes

Depending on local conditions and energy a power storage in the ratio 1: 1 to 1: 1.5 to the kWpeak power of the PV system is recommended.

A larger storage provides safety with increased consumption, more reserve in case of power failure and is more durable.

An example:

PV system with 8 kWp

Photovoltaic storage with a size between 8 to 12 kWh storage capacity.

Step towards energy independence. Be informed about saltwater electrical energy storage.

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