When an organization looks for a new or replacement access control system, the purchase price is often a principle factor when deciding on which system to purchase.
Purchase price alone is not an accurate measure as to the true costs of a system. When evaluating the products offered by different vendors, the purchaser should take into consideration: purchase cost of equipment and software; cost of installing the infrastructure including data cable and mains power outlet and power cables; cost of installation; cost of maintenance; cost of energy used over the projected life of the system; cost of disposal at the end of the products life cycle. It is only after costs associated with all of the above have been determined that the true cost of a system can be arrived at.
It is very difficult for the purchaser of a system to determine the true cost of a the system and its environmental and energy impact, because the purchaser will need to have a detailed technical understanding of the application, the products offered and the manner in which they are integrated. Energy costs will, without doubt, continue to escalate. Consequently, the cost of energy used by a system over its useful lifespan of say 7 years may be considerable. Users often consider the energy costs of lighting; heating and ventilation but almost without exception these are ignored when making a purchase of a CCTV, intruder or access control system.
Choice of Locks, Key to Reducing Lifetime Energy Cost
The choice of locks and power supplies (PSU) will significantly impact on the cost of energy used over the system’s lifetime. The following table gives a comparison of the energy used by the more common electric locking mechanisms tested:-
A magnetic lock will draw energy to keep a door locked. Many electric strikes also work in fail safe mode, continuously drawing power while the door is locked. Consequently, many locks used in access control applications are constantly using energy. Electric strikes used in a fail secure mode only use energy when unlocked; hence they are more energy efficient as they only draw power while access is being made.
Power Supplies, a Hidden Opportunity for Saving Energy
Power supplies are one of the crucial building blocks of modern system, converting high-voltage alternating current (AC) into low-voltage direct current (DC) for use by the electronic circuits in office equipment, telecommunications, and consumer electronics.
Between 6 and 9 billion AC/DC power supplies are currently in use worldwide. Power supplies not only convert energy – they also consume it. While the best power supplies are more than 90% efficient, some are only 20% to 40% efficient, wasting the most of the electricity that pass through them.
It has been estimated* that today's power supplies consume at least 2% of all electricity generated. Assuming there are 7.5 billion power supplies deployed worldwide, the application of more efficient power supplies could annually save nearly $9 billion in energy cost and reduce carbon dioxide emissions 72 million tons.
Linear power supplies, because they cost less to manufacture, are the most widely used power supplies in access control applications. Switched Mode power supplies work at much higher frequencies and are manufactured using solid state components. They are more expensive to produce, more compact and are substantially more energy efficient. A switching power supply will consume up to 50% less energy and also produce substantially less heat than an equivalent linear power supply. The energy efficiency of a power supply is determined by dividing the output power by the input power.
Typical energy efficiencies under load are in the range 25% to 60% for linear power supplies and from 50% to 90% for switched mode power supplies. This means that a door access system using a switched mode power supply could consume 50% less energy than an identical configuration using a linear power supply.
Building an Energy Efficient Access Control System
When planning an access control system, the correct choice of lock and power supply technology can make a significant impact on energy efficiency, cost of ownership and environmental carbon emissions.
