Faced with ever increasing energy costs and pressure to demonstrate their green credentials, organisations are examining all possible ways to reduce their power consumption. Claude Lyons’ PowerSave Energy Saving Regulator range offers a particularly efficient solution, with savings of up to 25% being possible. PowerSave also secures users against excessive mains supply dips, and its output, by being tightly phase balanced, can prevent equipment overheating and reduce maintenance costs.
Regulators reduce the electrical energy consumed on a site by reducing and stabilising its input supply voltage. Currently, the UK standard voltage as supplied from the National Grid is, in harmony with European Standards, specified at 230V ± 10% (207 – 253V). Accordingly, electrical equipment manufactured for the EU market is specified for 230V, or sometimes 220V, which was the previous EU voltage level. Meanwhile, for a variety of reasons the National Grid voltage hasn’t changed from pre 2007 levels, which were typically 240V or even higher. Although these fall within the 230V +10% -14% (197 – 253V) range permissible for EU equipment, they are unnecessarily high. This creates unnecessary energy losses as well as extra heating and stress in users’ electrical equipment. So voltage optimisation has a significant role to play in reducing the mains input voltage from 240V to 220V, or, depending on the load, 210V.
There is another mains supply factor of potentially great importance to electricity users. A report by economic consultancy NERA for Powergen stated that the UK could soon face power shortages. Closure of uneconomic, ageing plants and low investment could lead to electricity shortages in a severe winter. Energy generators could respond by reducing voltage levels during peak demand periods to reduce consumption. This contingency should be allowed for within any energy management strategy.
Within the Claude Lyons PowerSave energy saving regulators, the regulator output is user set to a site’s optimum voltage level. A servo amplifier uses the difference between the actual and desired output voltage to drive a motorised variable transformer. This applies a variable voltage to the primary winding of a buck transformer which in turn controls the voltage in the secondary winding. As the secondary is in series with the mains supply and the load, the load enjoys a stable supply regulated to within typically ±1% of its setpoint level. This design provides a fast, smooth, step less response with no added harmonics. It is also typically 99% efficient, partly because the control circuit operates only on the variable component of the mains input voltage.
Real example Figs 1 (Energy Saving Regulator) and 2 (Step Down Transformer)show why an energy saving regulator performs better than a fixed ratio step down transformer. In both cases, the objective was to ensure that the supply to the site did not dip much below 220V, making adequate allowance for voltage drops across the site. To achieve this, the transformer output must average over 228V; while the voltage regulator’s tightly controlled regulation allows an average of 220V without risk of unacceptably low voltage excursions at the user equipment inputs. Whereas the transformer yields an energy saving of 8.7%, the voltage regulator achieves 14.9%. On some sites, depending on their wiring and load conditions, larger voltage reductions and energy savings of up to 25% may be possible.
Because the PowerSave regulators maintain all three phases to within ±1% of their target level, their output is always phase balanced. This is important for some loads where unbalanced phases cause equipment overheating and shortened service life. And should the mains voltage unexpectedly drop because of grid capacity problems or any other reason, the regulator will maintain its controlled output, shielding the onsite load from external events. By contrast a fixed ratio transformer output will drop proportionally to the input voltage, even if this takes the load voltage below acceptable operating levels.
Not all loads benefit from voltage optimisation. Examples of such equipment include computers, communications systems and other IT hardware using switched mode power supplies, variable speed inverter drives, lighting with high frequency ballasts and thermostatically controlled items such as ovens, fryers and kettles. A detailed site survey which includes an estimate of expected savings before investing in voltage optimisation equipment is therefore essential.
However energy savings can typically be expected to reach 5 – 15%, with values up to 25% sometimes being achievable. And this is without the cost savings arising from longer equipment lifetime and reduced maintenance costs. The payback period is usually between 12 and 36 months. Reduction in carbon footprint can also be significant, as each kWh saved is equivalent to 0.43kg of CO?. Accordingly The Carbon Trust offers interest free loans to purchase PowerSave products. As these are repayable over up to four years, they are often covered by the energy savings. The regulators have essentially cost nothing to install.