The systemic energy audit: a key to energy efficiency in industry
A detailed examination of industrial processes is important for achieving maximum energy savings as these processes account for two-thirds of industry’s energy consumption. There are various audit methods available, including the innovative systemic energy audit.
Use less energy, introduce energy efficiency approaches… Many industrial concerns are already aware of these issues. And many have already made progress in these areas, especially through specific audits focused on their plants’ component “bricks”, such as switching lighting to LEDs, or installing variable speed drives, to quote just these two well-known solutions. Another type of audit, the systemic energy audit, makes it possible to consider new solutions. “Clients really want to take things to the next level now by focusing on the detail to see if there are still areas where savings can be made. This requires a complete overview that analyses the system in its totality. A systemic energy audit makes this possible”, explains Paul Dède, energy efficiency engineer at Actemium.
What does a systemic energy audit involve?
Why the term “systemic audit”? Because the industrial system is studied in its totality. Rather than focussing just on energy expenditure, the systemic energy audit looks at the quantity of energy needed to produce the end product, referred to as the minimum energy required, and makes sure that plant equipment capacities are adjusted accordingly. “We take the time to really look at the production process in detail by analysing all material and energy flows: steam, compressed air, cold, etc.”, explains Paul Dède. “For each process component, we analyse the match between material needs and the various types of energy involved.”
For each process component, we analyse the match between material needs and the various types of energy involved.
This audit reveals any inefficiency in the process, defines the performance indicators that are valuable for energy management and enables managers to take a fresh look at their production plant. “An energy audit generally focusses on the production of utilities, that is, the generation of steam at a given site, refrigeration unit consumption, etc., and on an analysis of complete energy bills”, says Paul Dède. “The systemic audit is unique in that it looks at the organisation globally. It interlinks the system components, contrary to the conventional approach that separates them.” It is not a replicable method. A systemic audit is always customised to suit a specific plant, with its particular processes. Now that regulatory audits have become mandatory, systemic audits take the energy efficiency process a step further.
Systemic energy audit: study the core of the industrial process
The first step in a systemic energy audit concerns the material transformation phases. “We examine the industrial process in detail to understand where the raw materials go. We then characterise all the transformations they undergo by comparing the energy used and the minimum energy required for the transformation to occur”, explains Paul Dède. “In short, we map the energy consumption at all workstations. We examine the sequencing schedules, utility yields, history of energy efficiency measures, distribution networks, etc.” This phase provides a detailed examination of energy consumption per gram of finished product, by cross-activity function (motorisation, compressed air, heat treatment, etc.) and by individual operation.
A performance plan is then put to the relevant industrial concern. It defines the Key Performance Indicators (KPI) that is crucial to the plant’s energy management. These KPIs match the energy consumed with the materials transformed in order to highlight the real energy costs associated with the product ranges.
The analysis of the KPIs and the minimum energy required also reveals where energy savings can be made, and can even reveal performance differences between two production lines operating under identical conditions.
What methods are used for a systemic audit?
The systemic audit is based on innovative methods used to determine if the potential energy savings is achievable. Actemium and PS2E develop and test in the field pinch analyses and energy studies. These methods aim to recover and use thermal energy at the scale of the individual industrial site and to adapt the sources of energy (electricity, gas, steam, etc.) to the process needs:
- the exergy analysis is used to match the material requirement (heat milk to 85 °C for example) with the most appropriate form of energy (steam, hot water, heat recovery, etc.).
- the pinch method is used to determine the potential for heat recovery from a given process. It is implemented to recover and use heat energy within a plant. In order to reduce energy consumption, the solutions recommended following this method may include reviewing the heat exchange network, incorporating heat pumps or even an ORC (Organic Rankine Cycle) process.
What concrete steps are taken following a systemic energy audit?
All the site’s requirements are taken into account when developing an action plan and proposing solutions. The minimum energy required for the transformation process cannot be reduced. On the other hand, the systemic audit can:
- detect waste: with the rollout of a performance tracking plan and raising employee awareness through training
- improve organisation and processes: optimise equipment and check operating conditions
- lead to remodelling and investment options: changes to facilities, recommendations for new equipment, etc.
For example, an audit performed by PS2E and Actemium in the food & beverage sector identified a 30% energy savings, mainly in the form of heat; and a 10% savings on the energy bill was detected in the hollow glass industry. In both cases, discussions are ongoing about how to incorporate the recommended solutions.
The regulatory systemic audit proposed by PS2E and Actemium has been endorsed as a regulatory audit. The systemic audit can transform the obligation to perform an audit into a dual benefit for the industrial client: it ensures compliance with the regulatory obligations and leads to measures being implemented that improve energy efficiency and reduce the energy bill.