Hi Guys,

I hope that you’ve all had a really great day.

Up to now we have looked at various aspects of renewable home energy solution, however there is a crucial element that we haven’t looked at yet: Energy Storage.

Most home energy solutions operate within a just-in-time system framework; that is during the day their solar panels and wind turbines produce electricity and any surplus produced is pushed back into the grid. At night, their reduced electricity production often forces them to draw electricity from the grid.

At best you consume as much as you produce and if you use more than you produce you still have you still have reduced electricity bills.

Although we are going to concentrate on photovoltaic cells for solar energy and wind turbines for home energy solutions I believe that if you have the space then it is advisable to store some of the energy you produce.

Without storage, you operate within a “just-in-time” framework that is not only dependent on your variable end-use demands, but you are also completely at the mercy of one of the most uncontrollable variables known to us: the weather. After all wind turbines are useful only when the wind blows and photovoltaic panels work only when the sun is shining. Energy storage is therefore needed to store surplus electricity produced at times of low demand.

To date cost-effective energy storage has been the orphan stepchild of alternative energy even though energy storage is a core enabling technology for many classes of alternative energy. Because of this power storage has been a key constraint in preventing the widespread adoption and use of solar and wind energy in general.

The trouble is that the period during which energy is generate from renewable sources, cannot always be matched to the time of demand. This leads to volatility in your supply and reduced reliability and stability. Energy storage systems are therefore an integral part of any renewable energy system especially if you go off grid.

Energy storage must consider both the amount of energy that can be stored (energy density of the material) and the efficiency at which it can be recovered.

Short duration storage technologies are frequently more important than long duration systems. In general, technologies that can store huge amounts of energy are not particularly good at releasing it quickly and technologies that can deliver energy quickly are not particularly good at releasing huge amounts of energy.

When an energy storage system is used you get stability within the electrical system and the quality of the voltage supplied will be considerably higher than under a just-in-time system.

From a user point of view there are both technical and commercial criteria for selecting the most suitable technology. This does not stop there though; because when one considers an electricity storage system one has to balance the technical with the economics and each case needs to be looked at individually. It ultimately all boils down to a return on your investment.

As far as energy storage goes conventional, commercially available lead-acid batteries have a very high-energy efficiency and all other energy storage technologies have to compete with this.

Batteries are the most expensive item in renewable home energy systems when considering the system’s total lifetime costs; and there are big variations in battery lifetime in different installations.

Rechargeable batteries or accumulators are the oldest form of electricity storage and are widely used. However, progress in battery technology has been slow.

Batteries can respond to changes in power demand within microseconds. Only super-capacitors equal such a response time. Batteries usually have very low standby losses and can have high energy efficiency, depending on the application and the details of the operation.

Most batteries contain toxic materials, hence the ecological impact from uncontrolled disposal of batteries must always be considered. Because of this current battery research focuses on new and improved materials and manufacturing processes, as well as on their operating conditions.

Ultimately the choice is yours on whether you operate a just-in-time energy system or whether you integrate an energy storage system into your home energy system.

One could start with a just-in-time system and gradually incorporate a energy storage system gradually to your home energy system with some the money you save on your electrical bill.

As always, I wish you everything I wish for myself.

Until the next time.

Alain

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