Energy Input Labeling

Obtaining Practical and Accurate EIL Measurements—Part II

Part I of this post discussed the energy inputs for compiling, writing and designing a book. Part II will concern the physical production hard copies of that book.

First we need to examine Direct energy inputs.

The book is printed on a good quality laser printer and comb-bound. The laser printer consumes energy from the local utility company power grid. The binding equipment only uses human labor. It punches the pages (with about 30 holes), collates the pages and covers, and stretches out and places the plastic comb.

The laser printer system comprises a combination CPU/monitor (an iMac) and a laser printer. The iMac is rated at maximum current of 6.75 Amps run at 120 V. Per the Standards, we use this maximum current rating. Arguably that is too high, but there are so many energy inputs that we are neglecting, that this is a reasonable approach. Further, the iMac and laser printer are substantial active while printing, so we are not greatly over-counting energy inputs. The laser printer runs at a maximum current of 5.5 Amps run at 120 V. This system must run for 15 minutes to product each book. So the iMac contributes 0.12 kilowatt hours (kWh or kwh) and the laser printer contributes 0.10 kwh for a total of 0.22 kwh.

Human labor is not trivial. Each booklet requires an average of 18 minutes, mostly spend during binding. Great care must be taken during the binding process, or the books become damaged. Using the baseline figure of 0.1 kwh energy input rate per person, per the Standards, 18 minutes of labor results in 0.03 kwh of energy inputs.

Therefore, direct Energy Added Inputs are 0.22 kwh + 0.03 kwh for a total of 0.25 kwh per book.

Next, we consider Indirect energy inputs.

These books are produced in an office setting, so indirect energy inputs for lighting HVAC (heating, ventilation, and air conditioning) need to be added. A fairly easy way to determine overhead energy is to take the total of energy used by the office, and subtract any energy that can be directly allocated to the production of products. Anything left over is indirect energy. For this reason, it is often easier to calculate direct energy inputs first. If a company produced more than one type of product, then indirect energy will need to be allocated to units of product on a rational basis, such as time required to produce each unit of product.

This small office consumes 100 kwh per month in overhead energy, and is staffed 160 hours per month, and spends 50% of its time producing books. Therefore, 50 kwh of indirect, overhead energy must be allocated to the books. If 3 books are produced per hour ( x 160 hours x 50%), the the overhead must be divided by 240 units of product (240 books). Since the  office spends 50% of its time producingbooks, then this proportion of overhead will be assigned to book production. So then, 100 kwh per month x 50% divided by 240 books equals 0.21 kwh of indirect energy inputs per book.

So then, the Direct and Indirect energy inputs per book are combined to report the total Energy Added Inputs we have per book, which here is 0.25 kwh + 0.21 kwh equals 0.46 kwh per book to produce the book. From Part I, we have 0.19 kwh required per copy of the book to compile, write and design the book. Adding 0.46 kwh + 0.19 kwh equals 0.65 kwh. So the book would be labeled "Energy Inputs Added: 0.65 kwh". The sources (and their percentages of contribution) could bereported as well.

Obtaining Practical and ...Part I–Fixed Calculations

The posting Obtaining Practical and Accurate EIL Measurements—Part I contained a misplaced digit resulting in several incorrect calculations. Those calculations have been fixed.

Kill A Watt plug load meter

Another plug load meter is the Kill A Watt series of meters, offered by P3 International. This series offers a range of meters from the Kill A Watt (tm) EZ simple plug load meter to the Kill A Watt (tm) PS electricity usage monitoring powerstrip. The EZ model was viewed for sale in the Brookstone (R) catalog. This site has not tried any of these meters yet.

"Plug Load" Meters

In the recent Obtaining Practical and Accurate EIL Measurements—Part I post, I mentioned devices that I could plug equipment into that would report the power usage. I was thinking about a particular meter that I've seen advertised, called Watt's Up. I've never used it, so I can't say if it's any good, but I plan to purchase one to try it out. Also, there are user comments for at least one of the Watts Up meters on Amazon.com. If any Energy Input Labeling readers have any experience with the Watts Up meters, please feel free to comment.

Obtaining Practical and Accurate EIL Measurements—Part I

Energy Input Labeling (EIL) is fairly new. The immediate goal is to provide ball park figures of Energy Added Inputs calculated and reported in good faith. Following the Standards helps to provide consistency.

Taking extremely scientific and accurate measurements may be very difficult for most businesses, especially small ones who are just starting out with EIL. This post discusses how I start out. This methodology is targeted towards business people, not engineers, so please do not get too offended by the roughness of the measurements. The calculations below may look scary, but with patience and a calculator, they will become fairly simple and second hand.

The product I have begun with was a short book that is sold commercially. The Energy Added Inputs by my firm include human labor to compile, write and layout the book. Energy used to produce the physical book itself is also included. I don't know the energy to transport the book, since I generally outsource that to the U.S. Postal service or other delivery firms.

I use a computer and a desklamp during these operations. I live in San Francisco, so I don't use much HVAC. My lamp burns a constant 0.060 kilowatt hours per hour. I know this because the lightbulb in my desk lamp states that it is a 60 Watt lightbulb. 60 Watts is not perfectly accurate despite the label, but it is a good enough ball park figure for now. I'll make even rougher assumptions later. 60 Watts x 1 hour = 0.060 kilowatt hours. (Note that "kilo" = 1000).

My body burns energy at a mean value of about 100 Watts. My body might burn more or less energy depending on whether I am out running around conducting field research or just sitting passively in front of the computer. Since I am not highly physcially active all of the time, I'll just use the baseline 100 Watt figure. So, 100 Watts x 1 hour = 0.1 kilowatt hours per hour.

How should I determine the energy input from my computer and printer? If I were an electrician, I could use special equipment to measure the actual current over a period of time, and the actual voltage if that varied much. This can be dangerous work! If you are not a qualified electrician, you should not use this method unless you can obtain the services of such a person. In my case, I do have the equipment (a volt meter and a current clamp), but I would have to rip apart my cable in order to accurately use the clamp, and I do not wish to do that.

There are devices that I could plug my computer into, and those would report the power usage. This may be a good alternative for businesses who wish to purchase such a device. If you use such a device, very carefully follow any safety instructions. Even plugging in and unplugging devices can be dangerous. Science education catalogs often sell such devices.

My computer has a maximum current rating of 1.875 Amps. Many items of electrical equipment are labeled with this information, particularly those that use wall current. It is often stated in the user manual. This figure is not the mean usage value, but the most the device is expected to use (such as during peak usage). An engineer would shudder, but I am going to use this as my energy input rate for my computer. Let's be clear. This figure tends to significantly overstate the energy input from this device. However, since I am understating or neglecting the energy inputs from so many other sources, I feel that this practice is not unreasonable and does not overstate the overall Energy Inputs. It is further justified by its ease of adoption and relative safety. My computer operates at about 120 Volts. So I multiple 1.875 Amps x 120 Volts to get an energy input of 0.225 kilowatt hours per hour. (Note: 1 Volt x 1 Amp = 1 Watt).

Say that I required 100 hours of time to compile, write and layout the book. Let's assume that I am using my computer and desklamp the whole time, or I am at someone else's office using at least that much energy. So my total hourly energy input rate is 0.060 kilowatts for the lamp, 0.100 kilowatts for my human body and 0.225 kilowatts for my computer, for a total of 0.385 kilowatts (or kilowatt hours per hour). The total time x input rate equals the input. So 100 hours of work x 0.385 kilowatts hours per hour is equal to 38.5 kilowatt hours (kwh). This is the total input to compile, write and layout the book.

However, say that I expect to sell about 200 copies of the book. It is of local interest, but is unfortunately not likely to be a national bestseller. I would call this a batch of books. Some firms would call this a "run" or a "Lot". I would then take the the above total input and divide it by the batch quantity, so that 38.5 kwh / 200 units of product equal 0.193 kwh per copy. If my book were a purely digital version and I outsourced distribution, I would be finished. The books could be labeled "Energy Added Input: 0.193 kwh". If the energy sources were known, they could be included as well. Here, the label would continue "Sources: 11% human energy, 89 % electrical energy". If the sources of the electrical energy were known, the figure for electric energy could be further refined, such as "11% human energy, 25% hydroelectric, 64 % coal electric".

Since physical copies of the book have been produced, will energy inputs in production need to be determined as well? Read the Standards (pdf) or wait for the thrilling answer in a soon-to-come future post!

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