Co-Generation

CO-GENERATION

Introduction

Cogeneration is one of a range of highly efficient energy technologies which provide the opportunity to both reduce energy operating costs, as well as the negative environmental impact of building plant operations.

Changes to the electricity industry and government policies throughout Australia, have resulted in Cogeneration systems becoming a financially attractive proposition for suitable site applications.

Cogeneration involves energy users producing a substantial proportion of the electricity they require on their own sites.

By adopting a cogeneration system a user may expect much lower overall energy costs. These savings are achieved in two ways, namely directly as electricity costs are reduced through partial replacement of supply with self-generated power, and indirectly as other fuel costs are reduced or eliminated by the application of waste heat for these purposes.

(Note: When generating electricity a significant percentage of the primary fuel source is wasted to atmosphere as heat. Cogeneration provides users with the opportunity to fully utilise the wasted heat for secondary activities, such as: space heating, hot water, process heating, and for other processes such as the provision of additional cooling by the use of absorption chillers.)

Cogeneration produces the best results in applications that have a constant and substantial heat load. Typical suitable commercial applications include: hospitals, hotels, shopping complexes, office buildings, swimming pools, and the like.

Examples of existing applications include several hospitals in Victoria, South Australia, and Western Australia, as well as an Aquatic Centre (Adelaide); City office tower (Sydney); Technical College (Sydney); and Parliament House (Sydney).

How Cost Effective and Efficient are Cogeneration Systems ?

A critical factor in establishing the cost-effectiveness of a cogeneration system for any building is the relationship between its heating and hot water needs and the electrical loads of the plant. Given the correct mix of heating and electrical loads, cogeneration can produce savings for typical buildings in the order of tens of thousands of dollars per annum.

Also as cogeneration systems are typically 75% to 85% efficient, which is up to 40% more efficient than conventional technologies, these systems can be significantly cheaper to operate than separate electrical supply and heating operations.

In some cases, in addition to displacing mains electricity, cogenerators can also sell surplus electricity back to the grid, thereby recouping their initial investment cost more quickly and thereafter generating a healthy financial return.

For established buildings, a cogeneration retrofit produces a better return on investment when the existing plant is due for replacement or upgrading.

However, the best savings are achieved when cogeneration systems are installed in the design stage of new buildings, as this enables a lot of the capital cost to be offset against services which would otherwise have been provided.

How to Test if Cogeneration is suitable for your Building Operations ?

Cogeneration should be considered if your building has a reasonably constant requirement for both heat and power during a normal operating day and throughout the seasons. The requirements may be for space heat, process heat or hot water.

If you can answer yes to one or more of the following questions, the case for cogeneration is even stronger. Do you:

Have reliable access to a cheap or waste fuel source?
Need to replace or upgrade your present boiler?
Need to install, replace or upgrade an emergency generating set?
Intend to initiate or relocate an industrial or commercial project to a greenfield site?

Prior to the application of a cogeneration system to a building, a detailed analysis of the central plant performance and operations should be undertaken by a qualified energy/engineering consultant, such as EMET Consultants.

These investigations should also be conducted under various stages of loading and at different times of the year to ensure the cost-effectiveness of the proposed system. For instance, a system which looks attractive under winter or full load operation, may not perform cost-effectively when the entire year's performance profiles are evaluated.

Your local electricity supply authority can advise you of likely interconnection issues and protection measures. In addition, the Electricity Supply Association of Australia (ESAA) has produced a very helpful document on Customer Cogeneration and Conditions of Interconnection.

Additional Benefits of Cogeneration

Cogeneration can also benefit the electricity supply industry and ultimately reduce the net cost of electricity by deferring future demand for increased transmission capacity and power station construction, as well as by expanding the diverse and geographical spread of electricity generation.

EMET Consultants can provide advice to those contemplating cogeneration and will help you at each step in developing a project to suit your operations. We also offer a comprehensive range of ownership and financing options which can be tailored to suit all types of sites and applications.

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