Can I heat water or the building by using electricity produced by the turbine?

Enthusiasts of small scale wind power have found a multitude of ways to utilise the power produced by the turbine. Some use batteries to store electricity for when the wind isn't blowing, others are grid connected, some are pumping water, others are charging electric vehicles, some are powering heat pumps, others are heating water and some are even doing a number of the above from one turbine. Furthermore there is any number of ways to do each of the above.

For a generator that is producing excess electricity, but not able to access the grid or avail of payment from electricity suppliers, storage is often considered.  Charged batteries hold the electricity in the form of chemical energy until it is needed and it is released once again as electrical energy.

Some microgenerators who can not avail of an export tariff opt for a system that will heat water. In this arrangement the electricity is passed through an element in a well insulated water storage tank. The electrical energy is converted to heat energy by the element and the heat is stored in the water tank to be used as needed. The water may need to be heated further by using electricity from the grid before use.

It should be noted that those with access to the export tariff of 9c/kWh or 19c/kWh should probably not consider the added expense of a water heating system from their turbine or microgenerator. Instead they should consider exporting the excess to the grid, receiving the payment, and import the required energy for heating on a reduced night-time tariff.

For those who do not have the option of an export tariff there are three main methods used to heat water from a wind turbine. One way is to just use a mains equivalent supply coming through the existing wiring loop from the grid connected inverter (or direct from an off grid controller) into the immersion element.

Another method is to heat the water via a small bank of wind charged batteries. The batteries provide a buffer from the fluctuations of the wind and provide low voltage direct current (12V, 24V, 48V) for a DC low voltage immersion element which would be a modification added to the well insulated hot water tank. This system could also be incorporated with an inverter and switching mechanism so that the load could be switched to mains voltage AC appliances in the house.

A third method would use a direct heating controller to heat the water tank with a switchover to either heat storage heaters at night or power the home during the day. This method has the advantage that batteries are not needed.

Careful consideration must be given to the method chosen. The demand profile of the premises and the size of the turbine are the key factors. Where no export tariff is available the goal is to design a system which will use every unit of electricity produced without the additional cost of storage.

Should I choose to add batteries instead of getting grid connected?

Batteries are used in off-grid or charging applications. Off-grid systems are employed when the cost of connecting to the grid is prohibitive or the customer chooses to remain off-grid. As off-grid systems don't have the back-up of the national grid to call on during times of low or no wind they need some form of storage if they are to have a constant source of electricity.

The capacity of the storage can be just enough to smooth out the short term variances in wind availability or it can be enough to provide power to the premises if there is no electricity produced by the turbine for periods of days. The amount of energy stored depends on the size of the generator installed, how long the customer wants to satisfy their on-site demand and on how much they are willing to spend on battery cells.
Batteries are an arrangement of cells. Cells can be purchased separately (e.g. 2 Volt) and can be assembled to create batteries of almost any required voltage (e.g. 24 Volt).

The type of batteries used with wind turbines are known as 'deep cycle' batteries (or deep discharge). These are not like car batteries which are designed to deliver a large current or be called on to deliver a large amount of energy over a short period of time, for example during ignition.

There are variations of deep cycle batteries which are less suitable for long slow charges and discharges such as 'leisure' and 'semi-traction' batteries. Full 'traction batteries' are the most suitable type of deep cycle battery and are the most commonly used in off-grid systems. They are the type used in fork-lifts and submarines. Electric fork-lifts are typically charged slowly overnight and depleted during the day which is close to the likely operation of an off-grid power system.

There are environmental issues to consider when looking at batteries. Much of the battery material can be recycled but elements such as lead and cadmium are toxic and their use should be minimised in the first instance even if they can be recovered. Batteries can be dangerous (explosive acidic fumes, liquid acid, shorting of terminals) and every precaution should be taken in safe storage and ventilation. Professional expertise should be employed.

Control of the charging and discharging of batteries is crucial if the batteries are to last a reasonable length of time. An expensive battery bank can be damaged beyond use if not employed correctly. Batteries need to be accompanied by a wind turbine specific charge controller to prevent damage as manual control with meters and switches is not a realistic option for most people. Most batteries are designed to deliver only a portion of the stored energy and not be discharged fully under normal operation. Full discharge will shorten the life of the battery considerably.

For grid connected wind turbines where the user has back-up electricity available in times of low or no wind, albeit at the retail price per unit, adding batteries is sometimes considered. It is considered when electricity suppliers will not pay for excess electricity exported on to the grid. If no payment is available then customers may wish to store the electricity for use later. The economics of such a decision need to be carefully considered however in light of the decision by ESB Networks and ESB Customer Supply to pay some categories of customer for exported energy. Payment to the remaining categories of customers is under consideration. When the export tariff is equal to or greater than the import tariff the grid effectively becomes a storage device- you sell to grid when you don't need it and buy it back when you do. When the export tariff is greater than the import tariff then there is a clear financial benefit to being grid connected over using batteries.

Battery storage is expensive and a well maintained bank may last only half as long as a good quality, well maintained turbine. Depending on the size of the turbine installed and the amount of storage required batteries can add €2,000 to €5,000 to a domestic scale system. Second hand deep cycle traction batteries have become increasingly difficult to source.

Can I get an import/export meter from ESB Networks?

The distribution system operator (ESB Networks) has made available, at no cost to the customer, 4,000 electronic import/export meters which are more intelligent than the standard electro-mechanical meter. These 'interval meters' should not be confused with the smart meters which will be piloted from 2009. The interval meters were made available as an interim measure to facilitate payment for export of excess power prior to a decision on a national roll out of smart meters. The availability of interval meters removes the key technical barrier to payment for export. The interval meter is necessary to access any available payments for exported energy. Interval meters will be supplied at no cost to the first 4,000 microgenerators applying over the next 3 years.

An interval meter is supplied automatically once you submit form NC6 to ESB Networks. Existing microgenerators who wish to be grid connected in accordance with current regulations should submit NC6 also.

Can I get a smart meter installed or how can I get involved in the smart metering pilot?

It is worth pointing out that the interval meter which is available from ESB Networks is different from the smart meter which will be piloted around Ireland in 2009/2010. The interval meter is existing technology and the smart meter will be a new technology with new supporting infrastructure. Microgenerators are not included in the smart metering pilot. The microgeneration field trials are separate from the smart metering pilot.

How do I go about organising a tie-in/connection to the grid?

Your chosen supplier could take care of the documentation necessary. It is a quick form so should be done at no extra cost. They should also take care of the hiring of a RECI or ECSSA certified electrician to carry out the connection to ETCI standards as part of their service.

Form NC6, available from the ESB Networks website, should be submitted well in advance of any grid tie-in.

NC6 is a straight forward one page form which includes:

• Name, address and co-ordinates of the site
• Contact details
• MPRN number
• Unique number assigned to each meter point
• Printed on the top of your bill
• Installer contact details
• Make, model and serial number of inverter (grid connected electronics)
• Declaration of conformance with "Conditions governing the connection and operation of microgeneration" including EN 50438.
• Details of generating unit
• Make and model
• Type of technology (wind, PV, micro-hydro, micro-CHP etc.)
• Unit Rating and phases generated
• Details of inverter unit.

Type-test certification for the inverter (the unit tying the system into the grid) should accompany the NC6 form. The certification required should declare conformance with EN50438 which is the appropriate standard for grid connected units. The suppliers should provide you with this paper work if you are submitting the NC6 form yourself.

You will need an import/export meter to avail of any payment for exported energy. The import/export meter currently available in Ireland is referred to as an 'interval meter'. It is now supplied automatically and for free to customers when they submit the NC6 form.