Moving Beyond Equipment and to System Efficiency: Massive Energy Efficiency Potential in Industrial Steam Systems in China

Author: Ali Hasanbeigi, Ph.D.

China is responsible for nearly 20% of global energy use and 25% of global energy-related CO2 emissions. The industrial sector dominates the country’s total energy consumption, accounting for about 70% of primary energy use and also country’s CO2 emissions. For these reasons, the development path of China’s industrial sector will greatly affect future energy demand and dynamics of not only China, but the entire world.

Sources: NBS, China Energy Statistical Yearbooks 2015. EIA, 2015

Steam is used extensively as a means of delivering energy to industrial processes. On average, industrial boiler and steam systems account for around 30% of manufacturing industry energy use worldwide. There exists a significant potential for energy efficiency improvement in steam systems; however, this potential is largely unrealized. A major barrier to effective policymaking, and to more global acceptance of the energy efficiency potential of steam systems, is the lack of a transparent methodology for quantifying steam system energy efficiency potential based on sufficient data to document the magnitude and cost-effectiveness of these energy savings by country and by region.

Source: U.S. DOE/AMO, 2012

In 2013-2014, I led a UNIDO-funded study to develop and apply a steam system energy efficiency cost curve modeling framework to quantify the energy saving potential and associated costs of implementation of an array of boiler and steam system optimization measures. The developed steam systems energy efficiency cost curve modeling framework was used to evaluate the energy efficiency potential of coal-fired boiler (around 83% of industrial boilers) and steam systems in China’s industrial sector. Nine energy-efficiency technologies and measures for steam systems are analyzed.

The study found that total cost-effective (i.e. the cost of saving a unit of energy is lower than purchasing a unit of energy) and technically feasible fuel savings potential in industrial coal-fired steam systems in China in 2012 was 1,687 PJ and 2,047 PJ, respectively. These account for 23% and 28% of the total fuel used in industrial coal-fired steam systems in China in that year, respectively. The CO2 emission reduction potential associated with the cost-effective and total technical potential is equal to 165.82 MtCO2 and 201.23 MtCO2, respectively. By comparison, the calculated technical fuel saving potential for industrial coal-fired steam systems in China is approximately 9% of the total coal plus coke used in Chinese manufacturing in 2012 and is greater than the total primary energy use of over 160 countries in the world in 2010.

Several sensitivity analyses were conducted, their policy implications discussed, and uncertainties and limitations of this study were presented in the report we published. Our report is published by UNIDO and can be downloaded from here. Please feel free to contact me if you have any question.

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Utilities large missed opportunity: Demand Response in manufacturing

Author: Ali Hasanbeigi, Ph.D.

Demand Response (DR) helps utilities to manage the peak electricity demand by temporarily shifting the demand on the consumer side instead of building new power plants to meet the short-time peak demand. On the other hand, customers use demand response to reduce their electrical cost using the time-of-use price signals. Nowadays, work is underway to automate the process using automated demand response (AutoDR).

In this post I will not get into the details of DR or AutoDR and rather discuss the DR potential in the manufacturing sector. I believe one of the main barriers to DR in manufacturing is that the DR potential in this sector is not well understood by utilities, companies and other parties involved.

Based on my experience on energy efficiency and demand side management in industry in the past 10 years, for a manufacturing sector or process to have a great potential for Demand Response (DR), it should have one or more of the four characteristics shown in the figure below.

Note: A bottleneck is a stage in a process that causes the entire process and the production rate of the final product to slow down.

Let me open this by giving a few examples below from an energy-intensive industry (cement industry) and a non-energy-intensive industry (textile industry).

Example 1- DR potential in the cement industry:

In a simple form, cement production process consists of raw material (mostly limestone) grinding, high temperature kiln for clinker making, and finish grinding of clinker and some additives into cement.

The electricity use in a cement plant ranges between 90 to 150 kWh/tonne cement depending on the grinding technology, raw material properties, etc. A cement plant may have a production capacity of less than 1000 tonne per day to more than 10,000 tonne per day. Therefore, the amount of electricity use by a cement plant can be quite substantial. Over 70% of the electricity use in cement plant is used in raw material grinding and finish grinding processes.

The raw material grinding process has the following three DR-friendly characteristics:

1. It is a batch process

2. It has large storage capacity for its output (ground raw material) which last for hours and often for days

3. The following process (which is kiln) can be considered a bottleneck of the production. This combined with large storage capacity before the bottleneck process (#2) provides a perfect condition for DR.

The finish grinding process has the following three DR-friendly characteristics:

1. It is a batch process

2. There is a large storage capacity after kiln for ground clinker (and before finish grinding), which last for hours if not days.

3. If production scheduling is flexible, the operation of finish grinding to produce the final cement product can be delayed for a few hours while the previous process can continue their operation.

If we assume that an exemplary cement plant uses 120 kWh/tonne cement of which 70% (84 kWh/tonne cement) used in raw material grinding and finish grinding, and produces 3000 tonne cement pre day (125 tonne/hour), every hour of shift in the operation of both raw material grinding and finish grinding in response to a DR signal will result in 125*84=10,500 kWh reduction in electricity demand.

This is roughly equal to average daily electricity consumption of 350 U.S. residential utility customers. If only the production of either raw material grinding or finish grinding is shifted, this reduction will be cut by almost half. This is such a large DR potential that I am going to hope all utilities and cement companies are taking advantage of it.

Example 2- DR potential in the textile industry:

There are many DR potential in the textile industry. I have done substantial work on this sector and can talk for hours on EE and DR potential in different textile subsectors and process. However, since this post is getting a bit longer than I planned, I will just briefly mention two DR potentials for this industry. If you like to know more, feel free to contact me.

The first example for the textile industry is in the yarn production process. One of the main process is called “spinning process” which uses different machines such as Ring frame, Open-end machines, etc. The spinning process has the following two DR-friendly characteristics:

1. It is a batch process

2. It is a bottleneck process. Often, intermediary products that are fed into spinning machines get lined up for hours on the plant floor waiting to be processed by spinning machines. Having a proper storage capacity will allow to store enough feeding product for spinning machines and shut down the previous process, which account for around 30%-40% of electricity demand of the entire yarn production plants, for few hours during the DR period.

Another significant potential for DR in the textile industry is in wet-processing plants. Wet-processing plants conduct preparation, dyeing, printing, and/or finishing of yarn and fabric and other textile products. Many batch processes exist in wet-processing plants. Also, several processes like dryer, Stenter, or batch dyeing machines can be bottleneck processes that provide DR opportunity. Often wet-processing plants work on several different orders and products; thus, proper production scheduling can provide great DR opportunity. To take advantage of this, there needs to be high level of coordination between different departments within a plant who are in charge of production planning, energy management, paying utility bills, etc. Figure below illustrate the concept of DR potential in production processes with batch processing, storage capacity and a bottleneck process.

To sum up, manufacturing sector is a complex and heterogeneous sector. Even within one industry subsector (for example, textile or food industry), there are completely different subsectors. However, there are great potentials for energy saving and Demand Response in the manufacturing sector. More in-depth understanding of production processes and technologies and energy systems in each manufacturing subsector will allow us to tap into these potential. 

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