BY DOUG REYNOLDS, EXECUTIVE DIRECTOR, NOTO
START BY IMPROVING EFFICIENCY
Although this series of articles is aimed primarily at tourism operations that generate their own power, usually with diesel generators, this information applies to you whether you generate your own electricity or buy it from the power company. No matter what your circumstances, the greatest and most immediate saving will come from simply reducing your consumption of energy.
I’m going to follow the advice of noted renewable energy expert Bill Kemp and avoid using the dreaded C word – conservation. Conservation carries the connotation of doing without or giving something up. What we are talking about here is improving efficiency – doing more with less. Replacing incandescent bulbs with compact fluorescents is an obvious example.They produce the same amount of light with about _ the electricity. You don’t have to stumble around in the dark or go back to kerosene lamps to reduce your electricity consumption – you need to look for ways to improve efficiency.
This principle applies to everything you use that consumes electricity. Refrigerators and freezers are probably another of your major electricity users, so you need to consider energy efficiency when you replace them.Heating devices like stoves, electric water heaters, clothes driers and electric heaters are among the least energy efficient devices out there. Replacing them with other energy sources like propane is an obvious first step in improving efficiency.
Some heating devices, like toasters and coffee makers, are difficult to replace. Though not very efficient, the good news is that they are operated for a relatively short time each day, so their impact is not nearly as great as some of your other appliances.
Getting your electricity consumption down to the lowest reasonable level is the most important first step in the process for another reason. Aside from reducing your operating cost for the system you are using now, this step will help you design whatever system you may move over to, such as solar panel or wind, at the smallest capacity necessary. Your electricity requirements will have a significant impact on the cost of a new system, so getting it down to the right value now is essential.
YOUR POWER REQUIREMENTS
When you decided what size diesel generator you needed, you only had to consider peak demand. You looked at everything you needed to run, and chose a generator that would do the job even if you had to operate everything at once. If you’re like most people, you then went up a size to make sure you had room for growth.
Motor driven generators are most efficient when operated near their rated capacity. Although fuel consumption goes down as the load is reduced, the generator still burns some fuel even when idling at no load. That’s why a 10kw generator uses less fuel to produce 10kw than a 15kw generator operating at part load.
If your exercise in improved energy efficiency does nothing more than allow you to reduce your maximum load from 14kw to 9kw, you will see a saving. If you’re ready for a new generator and you replace your 15kw with a 10kw, you’ll see even greater savings, both in capital and operating cost. But if you really want to see a big improvement in efficiency, you’ll need to go a step further.
A LESSON FROM TOYOTA
Everybody has heard the buzz about the new hybrid cars, like the Toyota Prius that get dramatically improved fuel economy. So how is it that hybrids improve efficiency as much as they do? It is an accepted fact that conversion of energy from one form to another always involves losses. A generator is less than 100% efficient in its use of energy, as is an electric motor.
Batteries are not 100% efficient either.
So how can using a gasoline motor to drive a generator to charge batteries and operating a car from an electric motor be more efficient than the old fashioned way of using the gas motor to drive the wheels? Let’s not forget about all the weight we have added with those batteries!
It turns out that modern electric motors and generators are pretty efficient, so we don’t lose much in the conversion to electricity and back to motion to turn the wheels. Here is the key – internal combustion engines, whether gas or diesel, are extremely inefficient. They are most efficient, however, near their maximum output.This is particularly true if their design is optimized for this kind of use.
A hybrid car runs the engine in bursts of full throttle operation whenever the power is needed to charge the batteries, and then shuts the engine off. This, along with other tricks like making the electric motor act like a generator during braking, results in the dramatic fuel economy improvement we see in hybrid vehicles.
A HYBRID POWER SYSTEM FOR YOUR LODGE
It is possible to use the same approach used by hybrid cars to improve the efficiency of the diesel generator at your lodge. Rather than using an AC generator to directly operate your lights and TVs and coffee makers, the generator would be used to charge a bank of batteries. Inverters connected to these batteries would convert the DC from the batteries to the AC you need to operate your normal lights and appliances.
Let’s consider your power demand over a 24 hour period. At peak periods, when water pumps are running to supply the showers, the toasters and coffee makers are going to prepare breakfast and the lights are on in the dining room, you may be running the 10kw diesel at near capacity. However,for much of the rest of the day, it is loafing along, generating a kilowatt or two.
With a hybrid system, the generator runs to charge the batteries and shuts down. In a typical installation, it might run for 5 or 6 hours each day during the peak demand period and to charge the batteries.After that, it shuts off until the next day, unless an unusual degree of electricity demand makes it necessary for it to recharge the batteries sooner.Aside from the obvious fuel saving, you have cut down wear and tear on the generator and eliminated engine noise for most of the day.
These systems have been quite extensively studied, and they generally reduce fuel consumption by about 35%. Of course,these savings come at some cost. You will require a bank of batteries with enough capacity to carry the load for the rest of the day, as well as inverters, charge controllers etc. The batteries require a certain amount of care and feeding, though this is generally pretty easy with modern batteries and chargers.
SIZING THE SYSTEM
Here is where all of our discussion about improving energy efficiency, and peak vs. average demand comes into play. Your inverters will need to be big enough to meet the peak demand of your operation. Because high quality inverters are not terribly cheap, getting your peak demand down to the lowest value possible will help control the cost here.
Your battery bank will need to be sized to handle your needs over the charging cycle period that you choose – probably 24 hours. The choice, care and feeding of batteries is a topic in itself, so we’ll devote an entire article to batteries. However, it is your average demand that will determine your battery requirements, so reducing your average demand will help cut the cost of this part of the system.
There is a good reason that we started with improved efficiency, and then talked about hybrid generation solutions as the place to begin. Aside from providing the greatest savings at the lowest cost, this is the essential starting point for a more elaborate system. If you want to further reduce your fuel consumption, other sources like wind, solar panels or micro-hydroelectric power can be used to charge the batteries. In any of these cases, the battery-inverter system you have put in place will form the basic core of your system.
Future renewable energy articles will look more closely at the economics and practicalities of these other sources of energy.
This article was taken from pages 13, 14, and 15 of NOTO's "The Outfitter" publication, Winter 2005 Issue