Process Heat systems are used extensively to provide heating for various industrial processes — essential to the daily operation of many companies. Such systems include indirect-heating steam boiler and hot water generator systems, as well as direct-heating systems such as gas-fired drying ovens.
This Audit Standard provides an approach to heating system auditing and analysis. The objectives of the standard are to:
a) Provide the framework for the systematic collection of data relevant to the efficient operation of heating systems; and
b) Enable the heating system auditor to analyse the performance of the system, identify potential energy savings and provide sound recommendations for implementation of energy efficiency initiatives.
In addition, includes a recommended report outline for the purpose of assisting concise, consistent and complete presentation of the analysis, findings and recommendations arising from a Process Heat system audit.
The scope of the Audit Standard is direct or indirect industrial heating systems, including distributed systems such as air, high-temperature fluids (e.g. thermal oil), steam and hot water systems, as well as direct process heating systems. Section 3.0 covers the on-site measurement requirements of an audit, while Section 4.0 covers the data analysis expected to assess the performance of heating systems.
Assessing the efficiency of a heating system amounts to assessing the system’s efficiency in fulfilling the purpose that the heating process is serving.
The boundary of the system concerned extends from the energy input to the heating system, whether via burning of a fuel or consuming electricity, to the point where the business purpose of generating the heat is achieved.
For example, that business purpose may be to provide heat for a cooking process (in the case of an oven) or to provide heat for a drying process (such as in the case of a lumber kiln) or to induce a chemical reaction. It is important to understand the ultimate goal of a process to ensure that any potential system changes are compatible.
The system boundary is therefore defined by the points beyond which any change to the system no longer has any effect on the business purpose that the system is serving.
This Audit Standard includes guidance on the expectations of audits conducted according to two generalised levels of accuracy requirements — a ‘base level’ and an ‘investment level’. These levels are representative of the two ends of an accuracy requirement continuum. Where on that continuum the audit fits is a matter for agreement between the auditor and the client, and will be determined by the client’s purpose in commissioning the audit.
The implications of measurement accuracy on audit accuracy are described in Appendix 4. The measurement and analysis applicable for an audit primarily intended to identify areas of inefficiency and opportunity in the system (a typical base-level audit) generally does not include extensive use of flow, pressure, temperature, fuel consumption and power measurement equipment.
A base-level audit may be the appropriate level to use to define the scope and measurement requirements of a subsequent investment-level audit of the same system.
While the Audit Standard does not specifically cover the skills required of the auditing party, the accuracy level requirement of the audit will have an effect on the level and scope of the skills required of the auditor.
Analysis of heating demand throughout a heating system requires the optimization of heat use. Solutions to improve the efficiency of this use include,
but are not limited to:
manual or automated isolation of heat users
scheduling of electrical heating system operation outside electricity network peak charge periods
reduction of heat or temperature consumption by users
reduction of pressure requirements by users
reduction of flow requirements by users
reduction in leaks, particularly relevant to steam leakage, direct heating and indirect high-temperature fluids such as thermal oil
improvement of heat-exchange surface
ensuring all system components are adequately insulated
utilization of lash steam within the heating system
Any improvement in the use of heat on the demand side ultimately reduces the energy input required from the system’s heating device. Calculations of fuel or power consumption reductions must take into account combustion and thermal efficiency. For base-level audits, reduction in fuel or power consumption can be calculated based on assumed combustion and thermal efficiency.
Potential recommendations should be assessed and evaluated using both technical and economic considerations. Where possible, recommendations should be selected and reported to the client before the supply-side study is undertaken so that feedback from the client with respect to the likelihood of any implementation can be factored into any supply side study.
