Assessing the Potential of Demand-Side Energy Management in the Cement Industry
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Date
2025-05
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Addis Ababa University
Abstract
Ensuring reliable energy access is crucial for sustainable development and economic growth. The
challenges posed by the growing energy demand can be approached through supply-side energy
management. However, this task has become increasingly challenging due to the high fluctuating
electricity demand and the growing share of intermittent renewable energy sources in the electricity
supply mix. In response to these challenges, demand-side management (DSM) has emerged as a key
strategy in modern energy systems to address grid stability, enhance energy efficiency, and promote
sustainability. This PhD study investigates an industrial demand-side energy management system,
focusing on improving energy efficiency, implementing demand response strategies and promoting
onsite power generation in the cement industry. The cement industry is notably recognized as one of
the most energy-intensive and emission-heavy industries. Hence, it is important to assess the potential
of demand-side energy management in this sector. The energy efficiency improvement opportunities
are explored with the help of a benchmarking tool, while a mixed integer non-linear programming
model is developed to evaluate the sector's energy demand flexibility, aiming to achieve energy
savings, grid balancing, and climate mitigation goals. The potential and viability of waste heat
recovery power generation are investigated by estimating the power output capacity, life cycle costs,
levelized cost of energy, and net present values for three different waste heat recovery technology
options.
The energy and environmental performances of the Ethiopian cement industry are first assessed and
compared against best practices with the help of a Benchmarking and Energy Saving Tool for Cement
(BEST-Cement). The results reveal that all the surveyed plants are less efficient, with an average
energy saving potential of 36% indicating a significant potential for energy efficiency improvement.
Then, potential energy efficiency measures (EEMs) have been identified and analyzed using a bottomup
energy conservation supply curve (ECSC) model. The findings show that the cost-effective
electrical energy and fuel-saving potentials of these measures are estimated to be 99 Gigawatt hours
per year which is about 11.5% of the plants’ annual electrical energy consumption and, 2.7 Petajoules
per year which is 12.5% of the plants’ annual fuel consumption, respectively. The cost-effective fuel
measures have an annual average CO2 emission reduction potential of 254 kilo-tonnes per year which
covers about 5% of the total CO2 emission. The technical potential for saving electrical energy and
fuel of the measures in each category amounted to 33% and 14%, respectively, of the annual energy
consumption of the surveyed cement plants. Sensitivity analysis is conducted using the key parameters
that show some discrepancy in the base case results.
To assess the energy demand flexibility potential of the cement industry, an energy consumption
optimization model of the industrial demand response for conventional power grids has been
developed, aiming to flatten the hourly demand curve of the grid by minimizing the industrial
customer's hourly peak loads and maximizing the shifting of demand to off-peak periods.The result demonstrates that the demand flexibility potential of the case study cement plants is about
495 MWh per day, constituting approximately 28% of the daily total electrical energy used by these
cement plants, proving that the cement industry is a potential candidate for demand response strategies.
By adapting the proposed model, the loads of the case study plants during the peak period of the day
are reduced by an average of 75%. In addition, an overall reduction of 188 tonnes of CO2 emissions
per day has been achieved in case study plants. Furthermore, the cost of consumed electrical energy
for a day decreased on average by 14% in these plants. Thus, the proposed model can minimize the
impact on grid instability and the cost of energy consumption of an industrial customer. Some
scenarios have been suggested in the study including the variation of the capacity factor, considering
onsite electrical power generation such as solar power plants and waste heat recovery power plants,
which can enhance the demand response obtained from the cement subsector.
Moreover, cement manufacturing is a highly energy-intensive process, with over half of the thermal
energy used in the production chain being lost. Consequently, exploring ways to capture and utilize
this wasted heat to generate electricity and meet industrial energy requirements is crucial. The study
investigates the potential for Waste Heat Recovery (WHR) power generation within the Ethiopian
cement industry. The levelized cost of energy (LCOE) and the Net Present Values (NPV) of the steam
Rankine cycle-based, Organic Rankine cycle-based and Kalina Rankine cycle-based waste heat
recovery power plant options are evaluated. The findings reveal that the steam Rankine cycle-based
waste heat recovery power plant is the only feasible plant in the Ethiopian cement plant, with the net
present value of 0.35 million USD, and about 0.04 USD per kWh of levelized cost of energy. The
power capacity of the feasible plant is about 8.9 MW for the studied cement plant with an annual
production capacity of 2.3 Mt of cement. This amount can cover roughly 18% of the case study
cement plant’s electricity demand.. The associated reduced CO2 emissions potential is not significant,
as the hydropower sources dominate the national power grid.
In summary, this doctoral research underscores the feasibility of adapting demand-side management
(DSM) strategies in the cement industry. The main findings are compared with similar studies and
international benchmarks, confirming the practical applicability. Detailed sensitivity analysis has been
conducted to ensure that the results derived from the base case assumptions remain reliable despite
potential fluctuations in the variations of influencing parameters. Consequently, this thesis can be a
valuable resource for energy policymakers and industry players seeking to develop effective DSM
strategies and policies. The methodologies and frameworks employed can be applied to similar
energy-intensive sectors worldwide, aiding in formulating DSM strategies for the energy system.
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Keywords
demand-side energy management, energy efficiency, demand response, onsite power generation, cement industry, benchmarking & energy saving tool, mixed integer nonlinear programming, energy conservation supply curve, waste heat recovery system, levelized cost of energy.