by Peter Jolly & Richard O'Sullivan
This paper was presented at the Solar 89 Conference. Australia & New Zealand Solar Energy Society.
Peter Jolly.
Energy Laboratory
Mechanical Engineering
The University of Queensland
St. Lucia. 4067, Australia
Richard O'Sullivan.
Applied Physics
Royal Melbourne Institute of Technology
Melbourne,
Australia
It should be noted that the trends and conclusions made in this analysis may not be accurate in the future as energy conversion efficiencies are continually being improved with advances In technology.
While it may be argued that fossil fuel technologies are nearing their maximum efficiencies, renewable energy technologies, due to their relative newness, can expect greater improvements in the ensuing decades. For example evacuated tubes offer great potential to produce medium/high grade heat while only having modest material energy requirements.
For example :
orders of manufacture
| order | |
| 1 | direct energy use |
| 2 | capital energy and fuel production energy |
| 3 | capital energy and fuel production energy to provide plant and fuel for order two |
Hot water heating accounts for approximately 35-40% of the energy consumed by a domestic residence.
SOLAR 89 CONFERENCE
Australian and New Zealand Solar Energy Society
ABSTRACT
This paper presents comparative data on the fossil fuel energy required to manufacture, Install and operate a solar hot water system and a RAPS System with their fully fossil fuelled counterparts.
The results show that both renewable energy technologies use much less energy than their counterparts to accomplish the same task over their lifecycle.
In the case of hot water heating solar energy Is more than 2000% energy efficient in Darwin and 250% efficient In Hobart.
The analysis shows that minimising the fossil fuel running energy requirements maximises the overall life cycle energy efficiency. This conclusion Infers we should consider using systems with higher solar fractions than previously recommended.
The paper highlights the shortcomings of comparing technologies solely on a cost basis.
| INTRODUCTION | ACKNOWLEDGMENTS |
| ENERGY ANALYSIS RULES | HOT WATER HEATING |
| REMOTE AREA POWER SUPPLY SYSTEMS | CONCLUSIONS |
INTRODUCTION
Often in debate on energy matters the question arises as to whether a certain technology requires more energy for its manufacture than it will produce during its lifetime.
Proponents of renewable energy technologies should be ready to answer such questions and be able to compare these technologies with fossil fuel technologies.
Comparing technologies on present economic grounds would be very short-sighted as the growing environmental movement will demand other criteria to be used which will include damage to the environment. cleanup costs and perhaps a resource tax.
This paper will use existing data to compare the energy required to manufacture, install and operate a flat plate solar hot water heater and a RAPSS (Remote Area Power Supply System) with their fossil fuel counterparts.
The study is only a preliminary one, pointing the way for a detailed follow-up study.
ENERGY ANALYSIS - SOME GROUND RULES
In order to assess the energy required to manufacture, Install and operate a device, such as a solar hot water heater, it is necessary to identify all the individual components and processes associated with the system. Several difficulties can arise when performing this analysis;
- Which figures do you believe?
Difficulty arises in determining the energy required to manufacture a given component.
For example, the energy required to produce copper sheet varies greatly depending on the grade of ore used. - Further, recycled metals, such as aluminium,
require less than twenty times the energy compared to "new" metals [3]. - Where do you draw the system boundary?
Production of a particular product, such as copper sheet, can involve many processes. These Include mining, smelting, casting and rolling with each step requiring inputs of capital energy (infrastructure), fuels, transport, labour..... and cat food f or the mine manager's cat!
Boustead and Hancock [2] describe a method of analysis which isolates various "orders" associated with the manufacture of a given commodity.
Actual analysis is seldom carried beyond order two, since further orders usually make an insignificant contribution to the overall energy consumption.
(see Sheridan,[4])
In the analysis presented here we are interested in comparing the total life cycle energy required by a fossil fuel system with a renewable energy system to achieve the same task.
Mathematically, the representation used in this analysis is as follows;
(equation 1)
T = C + nM + nR
- Where,
T = Total primary energy (fossil fuel) used to perform the task over the life of the device (kWh) - C = Total energy required to manufacture and install the device (kWh)
- M = Energy used in the maintenance of the device (kWh/y)
- R = Annual fossil fuel operating requirements (kWh/y)
- n = Life of device (y)
HOT WATER HEATING
Comparing the total life cycle energy required to provide hot water by electricity and solar energy.
This analysis compares the life cycle energy requirements of an electric boosted standard flat plate solar collector with an all electric system. One of the authors (O'Sullivan and Meldrum [5]) has undertaken a detailed study to determine the manufacturing energy requirements of a standard solar hot water system.
Table 1 summarises the total life cycle energy requirements for the two systems for capital cities in Australia.