Energy Consumption Calculations

By definition, power expressed in watts is equal to amperes x volts, and energy expressed in watt-hours is equal to amperes x volts x time (in hours). Therefore, the calculation of energy consumption requires a knowledge of the overall reaction and the number of Faradays required to produce the desired product, the operating cell voltage, and the cell current efficiency, which is illustrated here for the case of electrolytic chlorine production. The main anodic electrochemical reaction during the electrolysis of brine is the discharge of the chloride ions to produce chlorine, as described by reaction (4). When the chlorine current efficiency, ci2 is 100%, one Faraday of electricity will produce 

5 mol or 35.45 g of chlorine. Therefore, the number of coulombs required to produce 1 ton of chlorine will be  

If the cell current efficiency is less than 1, and has a value of cb. then 

Note that ECU stands for Electrochemical Unit or 1 ton of chlorine and an equivalent weight of NaOH. Table 4.4.1 gives the theoretical coefficients needed to calculate the energy consumption per short ton and metric ton of chlorine, NaOH, and KOH. 

The units of the energy consumption figures calculated using Eq. (5) are in DC kWhr/unit product. However, some chlor-alkali plants require data on the energy consumption expressed in AC kW hr/unit product, in which case the rectifier efficiency, rectifien has to be taken into account  

---

Electrochemical technologists routinely perform energy consumption calculations to understand and improve the economics of electrochemical operations and to compare alternative routes to products of interest. It is usually expressed in AC or DC kilowatt hours (kW hr) per unit weight of the substance produced electrochemically. Note that the electric utility companies charge the customers for the AC kWhr consumed in then-operations. 

For simplicity, Eq. (A3.2) is used to estimate the errors in the chlorine process efficiency and enei consumption calculations. The equation used for the energy consumption calculation is given by... 

Table 1,4.1 Voltage drop and energy consumption calculated at 96% current efficiency t = 960°C...

Energy Requirements. The energy requirements of several sodium manufacturiag processes are compared ia Table 7 (76). The data contain some ambiguities because of the allocation of energy to the coproduction of chlorine. An iadependent calculation shows a somewhat lower energy consumption for the Downs process (92). 

Two more consequences must be recognized about the very low pressure increases of 1 to 200 mm of water column made by the blowers. One is that those piressure surges, common in turbocompressors generating large pressure increases, are absent in these fans therefore, these can be operated at low flows. The second is that, in calculation of energy consumption and dissipation, the expression for incompressible fluids can be used even for gases. 

An electrodialysis cell has the following dimensions (110 cm X 60 cm x 0.04 cm (thickness), and is used to treat water with a throughput velocity of 10 cm/sec. The product concentration is 0.0092 eq/Liter. The cell current efficiency is 0.892. Resistance across the cell is 0.205 ohm. The influent concentration is 125 mg/Liter of NaCl. Calculate the following (a) cell current, (b) cell power output, (c) the cell voltage, and (d) the energy consumption per equivalent of product transferred. 

A filter s energy consumption, , based on average pressure loss, can be calculated as... 

LCC calculations frequently provide energy-efficient solutions. This gives reduced energy consumption and a reduction in environmental pollution. For example, the installation of a heat recovery system in a ventilation system may reduce the energy consumption and emissions by 50 to 80%. Figure 16.1 compares life cycle cost and life cycle assessment calculations. 

Caiciiiations can be sensitive to the interest rate (Fig- 16.2) and the time ol the calculation period (fig. 16.3), which is the utilization time or the life cycle of the device. Thus, it is often advisable to consider sensitivity analysis for these factors. Elements of uncertainty can also be found in the estimation of energy consumption and investment (in design phase at the pre-tender stage). 

LCCg = present value of energy cost Q = yearly energy consumption q = present energy price p = expected annual rise of energy price n = calculation period in years i = interest rate... 

Metabolic rate, basal (BM) Metabolic energy transformation calculated from measurements of heat production or oxygen consumption in an organism in a rested, awake, fasting, and thermoneutral state, in W nr. ... 

Using the values in Table 24.1 for body glycogen content and the data in part b of the illustration for A Deeper Look (page 759), calculate the rate of energy consumption by muscles in heaty exercise (in J/sec). Use the data for fast-twitch muscle. 

C06-0084. Using information in Figure 6-22. calculate the total world energy consumption in 1975. Then construct a pie chart showing the percentages of that total contributed by each major source. 

In total, for processing 1 ton of input waste, 99.4 kWh of energy is required. GHGs emission is calculated for energy consumption. It is assumed that electricity is taken from Vietnam electricity grid with an emission factor of 0.5764 ton CO2/ MWh [18]. 

To calculate the amount of hydrogen produced by electrolysis powered from a wind energy conversion system within a year, the efficiency of the AC/DC (or DC-DC ) conversion 0/c) and the energy consumption of the electrolyzer (ecel) per newton cubic meter of H2 production need to be defined. The efficiency of a standard AC/DC converter ranges from 80% to 95% [41]. High values of t]c occur in the conversion of large amounts of power. Typical values of ecel range from 5 to 6 kWh/Nm3. 

A 75 kg rower uses 52.5 kj per minute in a competitive race. Assuming that the race lasts 18 min, (i) calculate the total energy consumption during the race. 

---