In the continuing discussion of the electrical usage and costs of a High Volume Oxygen system, I wanted to share a modified configuration of the Lincoln Hot Glass system with different torches working on it. The configuration of the system and the torches working on it will affect the electrical costs. A larger system that needs to turn on fewer times to refill will have lower electrical costs than a smaller system that runs more often.
The HVO configuration for this graph is a MAX 60 gallon system with a 60 gallon storage tank and five 10 lpm oxygen concentrators (or 50 lpm).
How often is the system actually on?
For this scenario, a private class on two Alphas was taking place while another glassblower was working a highly oxidizing flame on a Delta Elite; one big torch working soft glass and two small torches working boro.
As the glassblowing session starts, an instructor is showing a student how to make a borosilicate implosion pendant on a Bethlehem Alpha torch. You can see the High Volume Oxygen System is nearing its low pressure set point (100 psi) to start refilling.
Follow the blue line to see the pressure and what times the system turns on and off.
The purple line shows how many liters per minute of oxygen are being used by the torches.
When the system turns on to refill, two Alphas are being used at the same time and continue to work while the system fills up. The usage of the two Alphas is fairly low (less than 25 lpm), so the system refills quickly. Just before it hits the high pressure set point (150 psi) to turn off, another torch is turned on. When the three torches are being used, the oxygen usage is a bit higher at between 30-40 lpm, so the system continues to refill but at a slower rate.
The second time the system turns on to refill (at 100 psi), the Delta Elite is pulling more oxygen (up to 70 lpm) than is being supplied (50 lpm), so the system loses pressure while everyone continues to work. The pressure is still high enough that all torches can work normally. In fact, the pressure never drops low enough that anyone needs to stop working.
When dinner time rolls around, everyone turns off the torches and heads home, and the system finishes refilling and then turns itself off.
So, how much money was spent on electricity over the course of the five hour period? Well, since we’ve got our handy Seeing Eye (TM) technology hooked up to the Lincoln Hot Glass system, we can see a lot of information about our usage and what is going on! Looking at the times that the system turns on and off lets us know how long the system was running.
The system was on and charging for a total of 257 minutes over the course of the 5 hour period in the studio from 2 pm to 7 pm. Hours in Use: 4.28
To find the electrical costs of running the High Volume Oxygen system, we need to start with the wattage of the components. The HVO System uses about 480 watts and each concentrator uses about 600 watts. We can take this information multiplied by the hours the equipment was running divided by 1000 to find the kilowatt-hours (kWh). Once we know this number we can use the energy costs in our area to determine how much we paid for electricity. In Lincoln, Nebraska, our residential $/kWh at this time is 8.9¢. (Of course, we’re located in a commercial space, but I’ll be using residential pricing and rounding up for the sake of showing the highest cost that you could expect.)
So, in this situation, the electrical costs of running the system for the duration of the session (5 hours) was $1.33. (The amount of oxygen generated was a little more than one and a half ktanks.) If you worked this way for 3 days a week, 48 weeks out of the year, your annual electrical costs would be $190, and you would generate the equivalent of roughly 230 ktanks!
Medium Studio System
In this scenario, the system is a medium system meant for a studio with two large torches running or a few small torches and one bigger torch. The last setup we have to illustrate is for a one person studio. (Coming soon…)
Part One detailing a large studio setup can be found here.