Energy Conversion Issues by Britt Storkson Owner, P2FlowLLC It is a fact, when converting one type of energy to another, there are losses in almost every case. These losses are expressed as a percentage (%) and are known as efficiency. For example, an electric motor converts electrical energy to rotational or kinetic (movement) energy. The typical energy conversion rate for an electric motor is about 60%, meaning about 40% of the electrical energy put into the motor is lost in the conversion process - in this case, mostly as heat. This figure can vary widely depending on the size and type of motor and the speeds (revolutions per minute) it is expected to operate at. Fluid pumping, which is converting kinetic or rotational energy to pressure (defined as force over an area) also has energy losses which again vary widely depending on the type of pump, the speed of the pump motor, and the rate of flow (gallons per minute) through the pump. This is also called efficiency. Pump efficiencies can range from less than 10% for low flow rate high-pressure pumps to close to 80% for low-pressure high flow rate pumps. Internal combustion engines convert chemical energy (gasoline, propane, diesel, etc.) into rotational energy at 20-30% efficiency. Most of the energy is lost out the tailpipe and as heat into the lubricating oil and cooling system. The only energy conversion that comes closest to 100% is electric resistance heating used in water and space heaters. Electrical resistance heating is also very desirable because it’s very simple and has no moving parts, so it is very reliable. Please note that while some of the above efficiencies are not very good, they are the best we can get given the physical limitations and the costs involved. We use internal combustion engines because, while the efficiency is fairly low, they are the best we can get given the physical conditions they need to work under (heat, cold, moisture, etc.) and overall cost of operation. Moving on to “alternative” energy sources, I’ve had difficulty finding efficiency figures for things like solar panels and electric car batteries. It’s probably because they are so low (bad) the manufacturers don’t want you to know what they are. When one charges a battery, one does not get the same amount of electricity back that they put into the battery. You always get something less - often considerably less because the charging routine itself takes energy as well. Let’s take a 12-volt lead-acid battery charging routine I’m familiar with and note the losses along the way. First, one needs to step down the voltage from 120 volts to 12 volts using a transformer. This is at least a 6% loss right at the start. Then the charging current needs to go through a full-wave bridge rectifier to convert the alternating current (AC) coming from the transformer into rectified AC or essentially Direct Current (DC). This introduces about a 1-volt loss - or about 8% of the power - just converting the power into direct current. So far we have lost about 14% (8% + 6% = 14%) of our power. Next, we need a way to switch the power on and off to the battery, which requires a switch of some sort. One could use mechanical switches which were used extensively in the early days of battery charging, but now semiconductors are often used. This is because they switch quietly and quickly and are more reliable because there are no moving parts. Despite the great advantages of semiconductors, they have a downside. They have a resistance which produces heat proportional to the current flowing through them. It’s also another ½ volt or so loss, so we’re looking at another 4% energy loss through the switching semiconductor. At this point, we have lost almost 20% of our power and we haven’t even got to the battery yet. Even electrical current moving through a metal wire requires energy. Did you know more power is used to get power to the location where it will be used than is necessary to power that location? This is fine as long as the power transmission equipment is sized correctly and provision is made for the heat rejection that happens, because electrical energy losses produce heat. So in almost every case, we need to spend energy to use energy. And the reason we have the energy delivery systems we have now is because it’s the cheapest, most efficient known way to move power from the source (generation) to where it’s going to be used. Most “alternative” energy sources have been tried and rejected years ago because they just didn’t “pencil out.” And that’s how we should evaluate everything. Britt Britt Storkson may be contacted via e-mail to michele@worldwidedrillingresource.com 32 OCTOBER 2024 WorldWide Drilling Resource® Congratulations Stewart Krause! 46 Years of Service and Dedication After a remarkable 46 years of dedicated service at Wyo-Ben, Stewart Krause has retired. His unwavering commitment and hard work have been instrumental to the industry. His legacy will continue in the hearts of those who have had the privilege of working with him. The staff and management of WWDR wishes Stewart all the best with his well-deserved retirement!
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