Retrofit : Retrofit Volume 2 Issue 2 2013
46 • RETROFIT AUSTRALIA • VOLUME 2 NUMBER 2 2013 | Lighting The business case for this upgrade is very decent, even before subsidies from energy efficiency certificate schemes. Single T5 luminaires can be installed for around $85. Based on an annual operating time of 3000 hours and a marginal electricity cost of 18 cents, the upgrade delivers an internal rate of return (IRR) of 36 per cent over a 10-year project life. The initial capital outlay is returned 3.7 times over this period. The 'payback' of this project is 2.7 years, but this unsophisticated measure of project financial performance is less than ideal. The addition of control systems will further benefit the project, essentially by influencing the amount of time the lights are on, rather than their power consumption. Control systems can be highly cost-effective -- automatically switching off lights when they are not needed is, quite frankly, a no-brainer, or should be. Control systems can include such elements as presence detection, daylight dimming, timers, building management systems and the like; however, any control system must be well commissioned. It must suit and be well liked by the occupants, so that they are not tempted to override the system or install incandescent desk lamps to compensate for poor lighting. The control system must work effectively and continue to do so. A secondary benefit that is often overlooked when assessing a lighting efficiency upgrade is the effect that the lighting system has on the building's air conditioning system. The waste heat generated by inefficient lights is extracted by the air conditioning system. If the cooling system has a coefficient of performance (COP) of three, then each kWh of heat generated by the lighting system places 0.33 kWh of electrical burden on the air conditioning system. Air conditioning systems in most parts of Australia are cooling buildings more often than heating, thus lighting systems do place a net load on the air conditioning system. Any lighting system installed should meet the Australian Standard for lighting design, which is AS/NZS 1680. The two key requirements of this Standard are that the lighting system meets minimum requirements for maintained illuminance (lux), and uniformity of illuminance (the variation of illuminance over the space). Other requirements of the Standard are to do with glare -- ensuring that lighting does not cause glare problems for occupants. The lamp colour temperature is also important (warmth or coolness of light), as well as its colour rendering index (its ability to faithfully reproduce colours). The lighting designer must also compensate for the inherent 'lumen depreciation' of lamps, as well as luminaires (due to dirtying of reflectors and diffusers). Thus, caution should be exercised when measuring the lux levels of an old lighting system versus a new lighting system. The new system should overcompensate the light levels by at least 25 per cent. As was hinted earlier, the business case for any lighting upgrade is a critical part of getting the project off the ground. Clients, decision- makers and company boards need to be convinced that projects are financially viable. The energy efficiency industry comprises more technical people than financial, and thus the unsophisticated financial metric that gets touted ubiquitously is 'payback'; however, the use of payback to describe project financial returns suffers from two major problems. Firstly, it lacks detail. It does not convey significant information about the profitability of the project -- it simply tells the decision-maker when the project will first return the initial investment; it does not communicate what occurs after that. Secondly, the energy efficiency industry, and subsequently its clients, has promulgated an obsession with achieving a payback of 'less than two years'. As was demonstrated in the case study examined earlier, a payback of 2.7 years is equivalent to an IRR of 36 per cent (analogous to an investment interest rate). Try getting that kind of return from a term deposit. Another useful metric is 'times money', which conveys that the project's initial investment is returned 3.7 times over its life. These two simple metrics are easily understood by non-financial persons, yet convey significantly more information, and are far more compelling, than payback. Beletich Associates is an Australian-based consulting firm focused on energy efficiency. The firm is led by Steven Beletich, an experienced consultant and energy efficiency advocate. www.beletich.com.au ...the business case for any lighting upgrade is a critical part of getting the project off the ground.
Retrofit Volume 2 Issue 1 2013
Volume 2 Issue 3 2013-2014