Contents
The Traditional Power Grid
The traditional power grid is a centralized model, consisting of a complex network of power lines that transmit and distribute electrical power generated at central power stations to the end-users. From the power plants, electricity is stepped up to high voltage (500kV, 275kV, 132kV) and injected into the transmission lines which transport electricity over long distances. At the end of the transmission lines are the distribution sub-stations which step down the electricity to medium and low voltage (33kV, 22kV, 11kV, 400V/230V) for distribution to end-users.
Sources of Power Grid Inefficiencies and Energy Losses
As the electricity flows through the grid, energy is lost due to system inefficiencies in the network. The different types of energy losses are listed below:
- Central Power Plant auxiliary power consumption. These are losses associated with the power plant’s internal usage to power auxiliary equipment such as pumps, compressors, cooling towers, transformer losses etc.
- Power losses in the transmission and distribution system. These are power losses associated with the electrical conductors, switch gears, transformers, etc.
- Energy Conversion Losses. These are the losses inherent in the energy conversion process from primary fuel, such as natural gas, oil, and coal, into electricity and can be further categorized as follows:
- Losses in the thermodynamic cycles.
- Losses in the combustion process.
- Mechanical losses in the prime movers (e.g., gas turbines, steam turbines, and internal combustion engines)
- Conductor and magnetic losses in the generators.
Source: IEA Report on Cogeneration (Combined Heat and Power)
The figure above (from the International Energy Agency) shows the energy balance in the global electricity system, providing valuable insights into the inherent inefficiencies and energy losses in the traditional power grid. The following table summarizes the inefficiencies and losses in the global electricity system as extracted from the IEA data:
| Gross Generation Efficiency = | 18307/49555 = | 36.94% |
| Energy Conversion Losses = | 31249/49555 = | 63.06% |
| Power Plant Own Consumption = | 1088/18307 = | 5.94% |
| Transmission & Distribution Losses = | 1596/17219 = | 9.27% |
| Primary Energy Efficiency = | 15623/49555 = | 31.53% |
The data from the IEA indicates that the Primary Energy Efficiency of the Global Electricity Supply is approximately 31.53%. In other words, for every one hundred MWhr of fuel energy consumed, only 31.53 MWhr of electricity is delivered to the final consumer, with inefficiencies and losses accounting for up to 68% of the primary energy input.
Malaysian Power Grid – Analysis of Power Grid Inefficiencies and Transmission & Distribution Losses
In the following discussion, publicly available data on the Malaysian Electricity Industry is analyzed to estimate the grid inefficiencies and Transmission & Distribution Losses in the Malaysian Power Grid.
Transmission & Distribution Losses in the Malaysian Power Grid
For the Malaysian Power Grid, the Transmission and Distribution Losses can be estimated from the latest edition of the TNB Sustainability Report (as of writing, the latest version is the 2021 edition). On Page 91 of the said report, the transmission and distribution losses as a percentage of total energy input to the grid can be tabulated as follows:
| Transmission and Distribution Losses for FY2021 | |
| Transmission*1 in Peninsular Malaysia: | 1.60% |
| Distribution*2 in Peninsular Malaysia: | 6.16% |
| Total Transmission and Distribution Losses in Malaysia as a Percentage of Total Energy | 7.76% |
| Definitions: *1 – Transmission is the process of transferring electrical power from power stations to substations *2 – Distribution is the process of transferring electrical power from substations to customers |
Another source of estimate for the Malaysian Power Grid transmission & distribution losses comes from the report, “Review on Electricity Tariff in Peninsular Malaysia under the Incentive-based Regulation Mechanism (FY2014-FY2017)” dated 19th December 2013, in which the transmission and distribution losses are stated as 8.5%.
Energy Conversion Losses in the Malaysian Power Grid
Energy conversion losses are accounted for in the calculation of the gross generation efficiency of power plants. The Malaysia Energy Statistics Handbook 2020 contains the “Energy Balance Table in 2018” (pages 48 & 49) from which the gross generation efficiency can be estimated for Thermal Power Plants in Malaysia, as follows:
| Power Generation Stations | Energy Input (ktoe*1) | Gross Generation (ktoe*1) | Gross Generation Efficiency (%) |
| Thermal Power Stations | 32,494 | 11,674 | 35.93 |
| Total of Above | 32,494 | 11,674 | 35.93 |
| Notes: *1 – Kilo tons of oil equivalent |
Primary Energy Efficiency of the Malaysian Power Grid
From the power grid inefficiencies and energy losses as discussed above, the overall primary energy efficiency of the Malaysian Power Grid can be estimated to be 31.90% based on the following assumptions:
- Transmission and Distribution Losses are approximately 8%.
- Average Power Plant auxiliary power consumption is approximately 3.5% of the gross generated power. It is estimated that the power plant auxiliary power consumption is in the range of 5%-8% of the generated gross power for a coal-fired thermal power plant and 2%-5% of the gross power of gas-fired combined cycle power plant. Taking the average of the “best in class” figures for thermal power plants provides an approximate value of 3.5%.
- The average Gross Efficiency of Power Plants is approximately 35.93%.
The Primary Energy Efficiency of the Malaysian Power Grid is estimated to be 31.90%, indicating that for every one hundred MWhr of fuel energy consumed, only 31.90 MWhr of electricity is delivered to the final consumer, with system inefficiencies and energy losses accounting for up to 68.1% of the primary energy input.
Role of Cogeneration in enhancing energy efficiency and reducing wasteful energy losses.
For Malaysia, Cogeneration offers a unique solution to achieving higher energy efficiency and reducing the inefficiencies and energy losses inherent in the traditional power grid. Cogeneration utilizes efficiently the waste heat from the exhaust gases of the prime movers (gas turbine generators and gas engine generators) to produce useful thermal energy, thereby typically achieving Primary Energy Efficiency of 80% or higher. Cogeneration systems, being on-site power generation solutions, offer the additional benefit of eliminating the wasteful energy losses found in the traditional model of transmission and distribution of electricity.