The profitability ofan idea is a quantitative measure. We take the 'return on investment. (ROI) and compare it with the specific ROI target that our customer has defined for investments. A typical value for a target ROI is two to three years. Profitable measures show an ROI below the target ROI, measures with an ROI above the customer. s target ROI are marked as not profitable. The ROI itself is calculated as the quotient of the investment for the implementation of a measure (in € or $) and energy saving gained by the measure (in € per year or $ per year). The investment will be estimated roughly in order to keep the effort low. That means we estimate the hardware costs and the customer contributes a so called 'multiplier' which takes into account costs for the implementation of the hardware in the plant. During the detailed design the calculation will be repeated with higher accuracy. The saving measured in € or $ per year will be calculated based on the data collected in the previous steps. It depends not only on the energy saving in kWh per year, but also on the energy price and the use of the plant. Therefore measures that are not profitable today can become profitable in the future when energy prices rise. Documentation of all measures and their profitability calculation is therefore a must.
Further investigation to estimate the investment or the savings derived from an individual measure must also be documented. This example may clarify the procedure:
• Projecttitle: Uselowpressuresteamforthegenerationofelectricity.
• Current situation: The plant produces low pressure steam in the range of 2050 th-1 depending on the load ofthe reaction step. As a basis for the potential calculation is medium value of 30 th-1 is taken. For the time being the low pressure steam with 2.5 bar (absolute) is condensed in four air coolers and fed into the condensate vessel.
• Project idea: Use of low pressure steam to generate electricity in a saturated steam turbine is proposed. The electricity can be used directly in the plant.
• Project description: A turbine should use 30 th-1 low pressure steam to generate 2334 kW. The condensation of the flash steam can be achieved at 0.35 bar (absolute) by the existing air coolers (approved by the provider). More than 30 th-1 steam cannot be condensed by the existing air coolers so that 30 th-1 is the design point. Minimum load of the turbine is 13 th-1 low pressure steam which should always be guaranteed. Load variation should not be a problem (information by the provider).
• Investment calculation: A turbine is offered by a supplier for1.1 M€ containing equipment as stated in the proposal (which is included in the documentation). The total investment is estimated with a multiplier of 3 to be 3.3 M€.
• Project economics: The savings are calculated to be 1.06 M€ per year and 79601 per year CO2. Investment and the savings result in a ROI of 3.1 years.
• Project rating: A detailed investigation of the project is necessary. Therefore the rating is B.
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