How Voltage Optimisers Reduce Energy Consumption

Voltage optimisation is the process of reducing the mains supply voltage on a site to a level that is lower than the voltage present at the incomer and at a high enough level to power on-site loads.

In the UK we have a higher mains supply voltage than most other parts of Europe. Our electrical infrastructure from the High and Medium Voltage (MV) generating stations and electrical distribution down to LV (low voltage) delivery provides a single-phase supply of 240Vac. Western European countries aim to deliver 220Vac.

When it was decided to create a harmonised supply across Europe of 230Vac, the easiest way to overcome the financial, technical and political barriers was to change the windows of acceptable generation to create a common overlap. The 240Vac window was changed to +6% to -10% and the 230Vac one to +10% to -6%.

Harmonising the electrical supply voltage provides benefits to hardware manufacturers who can design their power supplies to operate on 230Vac and within a set input voltage window. Care has to be taken however that the input window can accommodate both high and low mains voltage levels.

In the UK high mains voltages above 250Vac can be seen and especially so in more remote regions or those with a large number of local renewable power connections (both solar PV and wind turbine). The higher voltage levels leads to greater energy usage (and energy charges) and greater wear and tear on device power supplies. Worst-case hardware systems can shutdown when high mains voltages are present to protect themselves. Shutdown or automatic power-off can also occur when the there is insufficient voltage available from the mains power supply.

Voltage optimisers only help to reduce energy consumption when the mains voltage supply is high and above 245Vac. Ohm’s Law demonstrates this when considering that Power=IV Watts where I=Amps and V=Volts. For a device drawing 2.5A more power is required by the load at 250Vac than at 230Vac. Using voltage correction units to reduce the voltage supplied to the load, lowers the power consumption and therefore electricity charged for.

Voltage optimisation is proven voltage management technology and one recommended by the Carbon Trust to help reduce energy costs. Care must be taken and step-by-step process applied in order for the benefits to be realised. Firstly it is important to survey a site and identify the mains power supply voltage and load requirements. The site voltage and load profile can be monitored over time using data loggers and for large sites over as far a distance on the site as possible to assess voltage drop on long cable runs.

Once a profile has been identified for a given site, a correctly sized and specified voltage optimiser can be chosen and installed. The project can then be costed and the forecast energy savings compared to overall project costs and a payback period identified. Most voltage optimisers will achieve a payback within 5 years.

There are different types of voltage optimisation units including static and dynamic response units. Static VO units can include transformers (toroid or auto-transformers). Dynamic response units can include electro-mechanical servo and column-type voltage stabilisers. Once installed most VO units are maintenance free but should be inspected at least every year as part of a preventative maintenance program. The service visit is also useful as a way to check that the VO unit is correctly matched to the present voltage, load and site profile. Over the lifetime of a voltage optimisation unit, sites should expect both their load profile and the mains supply voltage to change. Other energy efficiency improvements can be made including the adoption of LED lighting, more efficient HVAC systems and inverter drives for pumps and motors. The electrical supply to the site can also change with more local demand increasing or being reduced.

Solar installations can also benefit from the use of a solar PV voltage optimiser and again only where the mains voltage available is higher than 245Vac. Solar PV inverters have to generate at a higher AC voltage than the mains power supply in order to export to the national grid. When the mains voltage is high, even at peak generation times a solar inverter may have to cut-out to protect itself as the mains voltage rises higher than its input voltage window. A solar PV voltage optimisation unit sits on the AC side of the solar installation and presents the solar PV inverter with a lower mains supply voltage.

At EcoPowerSupplies, our range of voltage optimisers includes VO units for domestic, commercial and industrial manufacturing sites from 60A single phase to 1MVA three phase. Please contact the Eco Power projects team for a free VO site survey and voltage optimisation assessment on 0800 612 7388.