Practical strategies to optimize power consumption in CBG plants

Electrical power is one of the key cost components in the operations of a CBG plant. In a typical plant operation Electricity charges can account for 40%-50% of the total direct costs. Optimizing these costs becomes vital to ensure long term profitability of the plant and driving towards the right levels Return on Investment (ROI). However, it is easier said than done because there are various operational aspects that one needs to look at to move towards optimality. Below are some of the practical approaches that could help in this direction

1. Motor Efficiency IE2 -> IE3.

Significant amount of energy is lost in the day-to-day operations of any motor. The loss builds on multiple fronts such as stator copper losses, magnetic core losses, ventilation losses and so on. While these losses cannot be completely eliminated, they can be reduced to certain extent. The efficiency class defined by IEC 60034-30-1 helps choose the right options. IE3 motors for example are 2-3% more efficient than IE2 motors. With rising power costs such improvements could definitely help mitigate the power costs.

2. Peak time tariffs versus off peak time Tariffs

Power tariffs are defined by the hour of the day which is typically categorized as peak, off peak hours. While peak hour tariffs are about 10-15% higher than the base tariff off peak hour tariff is about 10-15% lesser than the base levels. In a continuous operating plant like Compressed Biogas, it makes economic sense to utilize the off-peak hours especially for such equipment that have higher power ratings.

3. Pump selection

Different types of pumps are used for different purposes which is driven by the on-ground requirements. Solids percentage, operating pressure, volume flow per hour, negative suction etc., and many more such parameters determine the overall pump selection. Balancing the process flow requirements and these parameters can help optimize the overall power consumption in the plant.

4. Pretreatment

A well-cooked food held reduces the energy and effort required to break down the nutrition in any digestive system. Similarly, a pre-treated solution will help reduce the load on the mixing equipment within the digesters. Bringing down the viscosity of the input slurry can drive the power requirements to significantly lower levels.

5. Operations driven by Automation

Certain processes such a mixing etc. require specific number of hours of operations as per process design. Leaving such operations to the manual operators could lead to sub-optimal operating hours thereby leading to excess power consumption. Timer based automation can help control such slippages.

6. Power factor correction.

A phase difference can occur between the voltage and current waveforms. This phase difference leads to reactive power which can do no productive work but still drains out the energy from the source. Utilizing Capacitor banks in the system helps mitigate the losses. Such implementation is also subject to local norms of power distribution companies.

While these are some common approaches that can be applied for any plant some mitigation measures can further be explored specific to the location. Utilizing excess steam from nearby industrial zone , accessing solar or wind power along with advanced energy storage systems , utilization of Variable frequency drives is some of the additional options that could be explored with adequate planning and detailing there by reducing operating costs and adding to long term profitability.