An energy audit is an inspection survey and analysis of energy flow for energy conservation in a facility. The primary objective is identification of energy saving opportunities, a qualitative analysis of the implementation of energy saving measures and an estimation of its potential energy saving.
This article outlines just but a few practical energy conservation measures identified from previous energy audit assignments:-
- Retrofit of standard efficiency Motors with Premium high efficiency Motors.
We visited a facility whereby the motors in the facility were found to be comprised of IE2 /IE1 efficiency motors and there was no documented record on the frequency and the number motors had be rewound. We did a comparison of power consumption of all IE2/IE1 efficiency motors in the facility with similar rating and quantity of IE4 efficiency motors. Whereby the annual energy consumption is calculated as;
Annual Consumption = Rating (kW)*Quantity*Annual Working Hours*% Loading Efficiency (ղ)
Annual Energy Saving = Annual Consumption of IE2 Efficiency Motors – Annual Consumption of IE4 efficiency Motors.
The estimate annual consumption for the standard efficiency motors in the facility was about 549,413 kWh, whereas a retrofit of the standard motors at their end life with premium motors would have resulted in an estimate annual energy consumption of 524,658kWh. Therefore a retrofit would have resulted in an annual energy savings of 24,754.31 kWh, this translates to cost saving of about Kes 542,862 (US$ 5036). The estimate capital Investment on the IE4 Motors was calculated to be KES 2,355,000(US$ 21848), giving a simple back period of about four years and since the payback period is over two years we recommended a gradual replacement for the standard efficiency Motors when they reach their end life.
- Collection of rainwater from facility rooftop.
We visited a facility which used water from municipal supply for process, domestic and community usage. Harvesting rainwater from the facility rooftop was observed to be a viable option in reducing the amount of water bought from the municipality.
To be able to quantify the amount of saving for this particular project we looked up the geographical annual rainfall data for the area, from which using the estimated surface area of the rooftop we were able to estimated amount of rain water that would be collected annually.
The table above shows a summary for the techno-economic analysis for the energy conservation measure which had an attractive simple payback period of about one year.
|Taking roof surface area||
|M2||Surface area of the power house roof|
|Annual average rainfall in the area||
|mm||(data from Climate-Data.org)|
|Amount of rainfall collected in an year||
|litres||Amount of rainfall collected from the roof of the factory in one year in litres|
|M3||Amount of rainfall collected from the roof of the facility in one year in M3|
|Single phase pump||
|KSH||For pumping water to the storage tanks|
|2 Plastic tanks (3000litres)||
|KSH||Holding tank for rain water|
|Materials and Labour cost||
|KSH||Cost of laying pipes from the holding tank to the storage tanks|
|KSH||Total investment cost|
- Retrofitting the normal lighting with LED lighting.
A facility was found to have Compact Fluorescent Lights (CFL), T8 fluorescent lights, incandescent bulbs, and halogen and metal halide floodlights. These could be replaced by more efficient and durable LED lighting. We therefore recommended replacing them immediately with LED. To quantify the annual energy consumption and eventual savings we used the formula below;
Annual Energy Consumption = Rating (kW)*Quantity*Annual Working Hours
Annual Energy Saving = Annual Energy Consumption of Current Lighting – Annual Energy Consumption of LEDs.
A techno-economics analysis for the recommendation is shown below.
|Cost of energy saved in a year (Ksh)/ ($US)||
Taking the average cost per unit to be Ksh 21
|Simple Payback Period||
A facility was observed to consume a significant electrical energy from its processes translating to about 526 MWh Annually. This electrical power was supplied by utility company Kenya Power at an average cost of about 0.23$US/kWh.
Harvesting of renewable energy resources like solar PV has never been fully exploited within the facility despite them being abundant at the site.
We evaluated the potential in replacing part of the load with solar for possible energy savings.
A grid tied solar PV system without battery storage was proposed to be installed as an energy conservation measure.
A grid tied solar system is connected to a large independent grid (typically the public electricity grid) where it supplements the amount of energy imported from the grid by a consumer. This is a form of decentralized electricity generation whereby during the day the solar panels generate DC power which is fed into the PV inverter. The PV inverter convert the DC power into AC power which is then fed into the distribution board through a service box, typically a switchgear box. The power fed into the distribution board is then directed to the loads with any balance in supply being complemented by the utility grid. At night, all power being used is imported from the utility grid.
A techno-economic analysis for the design proposal showed that it would result to generation of about 146 MWh annually at an average cost of 0.13$US that would result to about 40% energy consumption saving.
A feasibility study for the proposed Solar installation using RET Screen Expert software showed a simple payback period of four years, 42.3 tonnes CO2 gross annual GHG emission reduction and an energy cost saving of Kes 81,370 802 / $USD 813,700 over the system lifetime, that is, at 100% debt ratio with a debt term of 10 years at 12% debt Interest rate.
- The other major energy conservation measures identified included:
- Repair and maintenance of the power factor correction equipment to avoid Power factor surcharge from the utility company.
- Installation of float switches and pressure sensors to start and stop pumps instead of operating them manually to avoid spillage and overflows.
- To carry out electrical inspection to ensure electrical standards are adhered in all the electrical supply and distribution systems thus improved power quality eventually resulting in energy efficiency.
- Fixing leaks from pumps and water systems
- Conducting Ultrasonic leak detection compressed Air system and fixing the leaks.
- Creating awareness to staff members to switch off lights in unoccupied rooms/offices.
- Avoid inappropriate uses of compressed air such as cleaning.