The heat of the summer probably provokes different thoughts in the general public than it does in electrical power professionals, including those involved in power quality investigations and energy audits. The following highlights just a few of the opportunities to help customers and increase cash flow.
Effects of increased HVAC
A number of factors contribute to the electrical cost of running an HVAC unit for cooling in the summer, including
- The real, fully loaded cost per kilowatt-hour
- The rated energy efficiency of the unit as compared to the actual energy efficiency based on unit age and maintenance
- The difference between the thermostat setting and the outside air temperature
The capacity of the system (in tons) versus the cooling load of the home, which includes number of rooms, insulation, number of windows (and their efficiency) and heating load from appliances and other equipment running for long periods.
While many of those factors can’t be altered by an electrical contractor, conducting an energy and efficiency study for a customer can determine if the HVAC unit is performing up to its rating. A week-long—or, even better, month-long—electrical energy monitoring study can be an eye-opener. It can demonstrate clearly to homeowners or facility managers the effect of HVAC usage on their electric bill.
Remember that utilities often have seasonal rates that mean increased summer bills. With newer smart meters, time-of-use charges may also be applied. In commercial and industrial facilities, there is usually a demand charge that can be set by peak usage during very hot days that will still be a penalty during other times when usage is drastically less.
Impacts on quality of supply
Many parts of the United States east of the Rocky Mountains experience thunderstorms in the heat of the summer. Lightning is a significant source of large impulsive voltage transients that lead to destruction of electrical infrastructure and equipment within a facility, as well as to the utility system in the rest of the nation. There are approximately 25 million lighting strikes a year in the United States, with damage and downtime costs in the range of $10 billion.
It doesn’t take a PQ monitor to know if a close lightning strike blew out chunks of Sheetrock, fried the electronic equipment or started an electrical fire. However, it can show what the impact is from not-so-close strikes, and whether the surge protection equipment (if there is any) is doing its job.
When those devices are subjected to repeated events, their capacity to divert the energy is diminished until there is no real protection left. Even if lightning doesn’t strike near a facility, it can cause a problem on the distribution system, resulting in voltage sag or sustained interruption. Advanced PQ monitors will show that the problem originated on the utility system, not within the facility.
The distribution system can also be affected by high usage during the heat of the summer. Ohm’s and Kirchhoff’s laws apply here, just like in every PQ situation. The increased current from high usage of HVAC loads results in increased voltage drop in the supply circuits. This leaves less voltage at the service entrance.
Constant power equipment running in a facility will increase the current draw to keep the power at the same level, which in turn causes more current on the distribution system. Increased heating in the wires causes them to physically sag, which may result in vegetation contact in improperly maintained areas.
Transformers can also overheat. To keep from overtaxing generators, sometimes utilities will reduce their output voltage, which used to be referred to as brownouts. This can become a downward spiral as the constant power equipment will react by increasing its current draw. If it gets severe enough, utilities may enact rolling blackouts or intentional interruptions.
By monitoring the voltage supplied by the utility, facility personnel see the effect on their equipment’s performance and efficiency during reduced voltage situations and can take steps for an orderly shutdown of equipment, if necessary. Where backup power sources are present, personnel can also determine if they switch over at the proper times and keep critical equipment adequately powered.
Peak solar panel performance audit
The output of fixed solar panels on the roof of residences and commercial/industrial buildings is likely to be at its highest during the summer months when there is longer daylight and the sun is at an optimal angle to the panels. Monitoring the current flow quantity and direction can show whether the system is producing the financial benefits that were stated when the system was installed.
Thanks to the Lovin’ Spoonful for paraphrasing its song, the summer is time to increase your revenue with the heat.
stock.adobe.com / VectorMine
About The Author
BINGHAM, a contributing editor for power quality, can be reached at 908.499.5321.