Energy Management Fundamentals

Cheatsheet Content

### Energy Conservation - **Definition:** Reducing the quantity of energy consumed by using less of an energy service. - **Importance:** - Reduces environmental impact (lower greenhouse gas emissions). - Decreases energy costs and improves economic efficiency. - Enhances energy security by reducing reliance on external sources. - Preserves natural resources for future generations. ### Power Factor Correction - **Problem:** A factory has a load of $100 \text{ kW}$ operating at $0.7$ power factor lagging. Improve it to $0.95$. - **Calculations:** - Initial Power Factor $(\cos\theta_1) = 0.7$ - Initial Apparent Power $(S_1) = P / \cos\theta_1 = 100 \text{ kW} / 0.7 = 142.86 \text{ kVA}$ - Initial Reactive Power $(Q_1) = P \tan\theta_1 = 100 \text{ kW} \times \tan(\arccos(0.7)) = 100 \text{ kW} \times \tan(45.57^\circ) = 100 \text{ kW} \times 1.02 = 102 \text{ kVAR}$ - Target Power Factor $(\cos\theta_2) = 0.95$ - Target Angle $(\theta_2) = \arccos(0.95) = 18.19^\circ$ - Final Reactive Power $(Q_2) = P \tan\theta_2 = 100 \text{ kW} \times \tan(18.19^\circ) = 100 \text{ kW} \times 0.328 = 32.8 \text{ kVAR}$ - Required Capacitor $(\Delta Q) = Q_1 - Q_2 = 102 \text{ kVAR} - 32.8 \text{ kVAR} = 69.2 \text{ kVAR}$ - Final Apparent Power $(S_2) = P / \cos\theta_2 = 100 \text{ kW} / 0.95 = 105.26 \text{ kVA}$ ### Energy Audit - **Definition:** A systematic inspection and analysis of energy use and flows in a building, process, or system to identify opportunities for energy reduction. - **Main Objectives:** - Identify actual energy consumption patterns and costs. - Pinpoint areas of significant energy waste. - Evaluate technical and economic feasibility of energy-saving measures. - Recommend cost-effective energy efficiency improvements. - Establish a baseline for monitoring and verifying energy performance. ### Motor Energy Calculation - **Problem:** A $20 \text{ kW}$ motor operates $8 \text{ hours/day}$ for $25 \text{ days}$. Cost = $Rs. 30/\text{kWh}$. - **Calculations:** - Daily Energy Consumption $= \text{Power} \times \text{Hours/day} = 20 \text{ kW} \times 8 \text{ h/day} = 160 \text{ kWh/day}$ - Monthly Energy Consumption $= 160 \text{ kWh/day} \times 25 \text{ days} = 4000 \text{ kWh}$ - Monthly Cost $= \text{Monthly Energy Consumption} \times \text{Cost/kWh} = 4000 \text{ kWh} \times Rs. 30/\text{kWh} = Rs. 120,000$ - $15\%$ Savings $= 0.15 \times Rs. 120,000 = Rs. 18,000$ ### Motor Energy-Saving Techniques - Use of **High-Efficiency Motors**: Replace old, inefficient motors with new, higher-efficiency models. - **Variable Frequency Drives (VFDs)**: Implement VFDs for applications where motor speed varies, allowing the motor to operate at optimal efficiency for partial loads. - Proper **Motor Sizing**: Ensure motors are correctly sized for their application to avoid operating at low loads where efficiency is poor. - Regular **Maintenance**: Keep motors and associated equipment well-maintained to reduce friction and improve performance. ### Load Factor - **Problem:** A factory consumes $48,000 \text{ kWh/month}$ with max demand $120 \text{ kW}$. - **Calculations:** - Hours in a month (approx.) $= 25 \text{ days} \times 24 \text{ hours/day} = 600 \text{ hours}$ (Assuming 25 operational days for consistency, or $30 \text{ days} \times 24 \text{ hours/day} = 720 \text{ hours}$ if continuous) - Average Load $= \text{Total Consumption} / \text{Hours in month}$ - If 25 days: $48,000 \text{ kWh} / 600 \text{ h} = 80 \text{ kW}$ - **Load Factor:** (Average Load / Maximum Demand) $\times 100\%$ - Load Factor $= (80 \text{ kW} / 120 \text{ kW}) \times 100\% = 66.67\%$ - **Comment:** A load factor of $66.67\%$ indicates that the factory is not utilizing its maximum demand capacity constantly. A higher load factor suggests more efficient use of the installed electrical capacity and can lead to lower electricity costs per unit of energy consumed. ### Demand Side Management (DSM) - **Definition:** Strategies and programs implemented by electricity utility companies to influence customer electricity consumption patterns to achieve desired changes in the load shape (e.g., reducing peak demand). - **Objectives/Techniques:** - **Peak Shaving:** Reducing electricity use during peak demand periods. - **Load Shifting:** Moving electricity use from peak to off-peak periods. - **Strategic Conservation:** Promoting long-term energy efficiency and conservation. - **Demand Response:** Incentivizing consumers to reduce consumption during high-price or system stress events. ### Illumination Calculation - **Problem:** Illumination required $= 250 \text{ lux}$ over $120 \text{ m}^2$. Each lamp $= 2500 \text{ lumens}$. - **Calculations:** - Total Luminous Flux Required $= \text{Illumination} \times \text{Area} = 250 \text{ lux} \times 120 \text{ m}^2 = 30,000 \text{ lumens}$ - Number of Lamps (theoretical, assuming 100% utilization factor and no losses) $= \text{Total Luminous Flux Required} / \text{Lumens per lamp}$ - Number of Lamps $= 30,000 \text{ lumens} / 2500 \text{ lumens/lamp} = 12 \text{ lamps}$ - **Suggested Improvement:** - **Consider Maintenance and Utilization Factors:** In reality, the number of lamps needed will be higher due to light losses (dust, aging, room shape, reflection). Apply typical maintenance factor (e.g., 0.8) and utilization factor (e.g., 0.6-0.8) to get a more realistic number. - **Use LED Lighting:** Replace traditional lamps with energy-efficient LED lamps to reduce power consumption while maintaining or improving illumination levels. - **Optimize Layout:** Strategically position lamps to ensure even light distribution and avoid dark spots or over-lit areas. - **Implement Daylight Harvesting:** Utilize natural light where possible and integrate lighting controls (dimmers, sensors) to reduce artificial lighting when sufficient daylight is available.