Voltage Optimisation FAQ

Q: What is Voltage Optimisation?

A: Voltage optimisation aims to reduce electricity usage, power demand and cost by reducing supply voltage received. It can improve power quality by reducing harmonic and transient voltages, as well as balancing phase voltages.
A reduction and balancing in electricity supply voltage achieves a saving in energy consumption (kWh) and a reduction in maximum demand (KW & KVA).

Q: Is Voltage Optimisation the same as Power Factor Correction?

A: No. They work in different ways and are complementary technologies.

Q: Why does Voltage Optimisation save energy?

A: Typically the electricity network supply voltage is higher than the optimum design voltage for AC motors resulting in excess energy use (kWh) and maximum demand (kVA).
By stabilising the supply voltage at the optimum voltage for the equipment, energy cost savings can be achieved for a large proportion of a sites electrical equipment.
Voltage sensitive equipment is the target for voltage optimisation related energy saving.

Q: Does Voltage Optimisation work for all equipment?

A: No, because some equipment is more voltage sensitive than other equipment and some not at all.
For instance, any equipment that is converting Alternating Current (AC) to Direct Current (DC) is not normally voltage sensitive, and voltage optimisation will deliver no energy savings. Examples of this type of equipment includes LED lighting, personal computers, flat screen TV’s and inverter air conditioning.

Q: What are some examples of voltage sensitive equipment?

A: Voltage sensitive equipment includes AC induction motors found in refrigeration and air-conditioning (HVAC) systems, pump and exhaust fans and the now rare older types of lighting, for example halogen and incandescent.
Somewhat voltage sensitive equipment includes variable frequency controlled motors. These will deliver significantly less energy consumption and cost savings than if not VFD controlled.
Note: VFD is also often called VSD as the frequency controller is varying the speed of the motor.

Q: What pieces of equipment are not suitable for Voltage Optimisation?

A: Some motors have a nameplate design voltage of 430V at 50Hz and are therefore not at all suitable for voltage optimisation.
This is rare and generally only found in a small number of Refrigeration compressors and smaller air conditioning compressors that are generally Bitzer branded equipment.

Q: Will Voltage Optimisation damage my equipment and reduce its life expectancy?

A: Not at all. In fact, properly implemented Voltage Optimisation will reduce the heat generated within electrical equipment such as motors and therefore enhance the equipment’s life expectancy.

Q: How does Voltage Optimisation effect motor performance?

A: A typical motor performance curve, as shown below, demonstrates that current in a motor is higher when the supply voltage is either higher or lower than the optimum design voltage.
Therefore, by optimising the supply voltage, we are improving efficiency, reducing losses and reducing energy consumption (kWh) of the motor/s.

Image source: Cowern papers

According to NEMA, motors are to be designed for “normal” operation for supply voltage in the range of +/-10% of design/nameplate voltage. So small variations in voltage should do no harm.

Q: What is the purpose of the Captech Voltage Optimiser?

A: The Captech Voltage Optimiser will balance and stabilise phase voltage reducing losses in a three phase motor due to out of balance voltage.

Q: What is the effect of out of balance voltage?

A: Out of balance voltage can have a significant heating effect in motors, with consequent reduction in equipment life.

Q: How will I know if Voltage Optimisation is suitable for my site?

A: If your site has a relatively continuous use of electrical motors and this is a significant proportion of your total energy consumption then your site is likely to be worth investigating.

Q: What are some examples of sites that use Voltage Optimisation?

A: Supermarkets and cold storage sites can expect good results from voltage optimisation. Moreover, sites with a high proportion of air-conditioning HVAC (non-inverter type) are also generally a good saving opportunity, subject to the customer’s ROI benchmark. Many other sites, such as process plants, are another possible opportunity for energy saving from voltage optimisation.

Q: How do Captech develop a business case for energy saving at my site?

A: There are five key steps involved in creating a business case for energy savings from voltage optimisation, as outlined below:

  1. Analysis of 12 months of electricity meter interval data and at least a current electricity bill to develop a feasibility business case. From this, we can establish to total energy consumption for the 12 months as well as the maximum demand in KVA for the site. The KVA enables us to size the VO unit capacity.
  2. Installation of a voltage data logger that will gather the average, maximum and minimum voltage over approximately seven days.
  3. Determining the energy consumption breakdown for a site by reviewing any previous energy audit reports, using known industry standard breakdown and or by agreement with the customer following a site inspection.
  4. Applying the energy data, average supply voltage to our benchmarks of saving by equipment type to determine a conservative estimate of energy saving for the site.
  5. Conducting a site inspection to confirm the equipment voltage rating as well as to investigate where both electrically and physically a voltage optimiser could be installed. This leads to an estimate of installation cost and whether an outdoor or indoor unit is required.

Q: What information do we need to start developing a business case for your site?

A: Before we proceed in investing our time and cost in establishing a business case for you, we really need to understand what you want to achieve. Sometime this information also drives what type of VO and or other technologies to recommend in your solution. Consider for example:

  • Is cost reduction the only or primary driver?
  • Is it environmental impact reduction/sustainability?
  • What is your minimum investment criteria? e.g. Return on Investment, %ROI or Simple Payback in years.
  • Procurement process. Is this just to set a budget or a firm price proposal for immediate progress to project approval? What might be the normal decision making timeframe?
  • Do you want us to incorporate a finance offer designed for positive cash flow, with a structure like Lease payments, hire purchase, rental etc.?

Q: What technical information do you require for a Voltage Optimisation business case?

A: You must have:

  • 12 months of electricity meter interval data showing at half hourly intervals kWh, KVA and Power Factor. This is normally obtained from your electricity retailer. We can obtain it for you if you have provided us with a “Letter of Authority”. (We have a draft LoA available if you wish)
  • At least a current electricity bill, preferably 12 months of bills.
  • Any known future electricity contract rates as shown in your contract with your electricity retailer.

Q: Is there any other information that would be helpful to obtain?

A: It would be helpful if you have some or all of the below information:

  • Single line diagram of the main electrical switchboard. Don’t worry if you don’t have one as that is pretty common. If you have one it can save us a lot of time.
  • A floor plan of the site showing where the main switch room and mechanical plant room. Again this is optional, but can save us some time.
  • Previous energy audit reports.
  • Recent or planned upgrades or replacement of electrical equipment.
  • Site contact for us to set up a site visit/inspection.