Monitoring the ESD performance of a sustainable multi-residential housing development in Melbourne
Project Reference: 398A2
Industry or sector: Multi-residential
Utilities and energy use: Electricity, gas, water, thermal, solar
Date added: August 2013
Abstract: Monitoring the performance of a sustainable multi-residential housing development in Melbourne
Genesis Now project manager: Rob Alexander, Senior Energy Efficiency Engineer
The project owner wanted to build a block of 96 apartments with a more sustainable design than the then-current standard for public housing, in terms of reduced use of electricity, gas and water. Targets were set which the design was expected to meet. Once the buildings had been constructed and occupied, the question was: how well (or badly) were the sustainable installations performing in comparison with the targets set? Genesis Now was engaged to check on the purchased utilities (electricity, gas and water) as well the on-site contributions from the solar hot water panels and solar photovoltaic (PV) electrical energy, and to compare the actual performances to the design targets.
Overall, while most of the target performance parameters were being achieved, some were not. This is shown on graphs by using a green background for achieved targets, and a pink background for unmet targets. Most of the charts show three results are shown; from the left:
- that considered typical of previous design using gas heating or “Standard Dev’t (Gas Heating)” shown as 100%,
- the target for the building at the design stage or “Design Target”, and
- the actual achieved performance or “Achieved”
The first problem encountered was a lack of information: for instance, the development has rainwater as the primary source for domestic hot water and treated greywater as the primary source for toilet flushing and landscaping, however it was not possible to measure their contribution. Genesis Now recommended the installation of six additional meters to allow tracking of the various water sources. The six meters were; two for domestic hot water (rainwater and mains), two for toilet flushing water (treated and mains) and two for landscaping (treated and mains).
Overall, annual performance is shown below. The mains water use was below the target value.
Records showed that the recent annual contribution of rainwater to domestic hot water was only 22%, and only up to 50% in a recent high rainfall month. Following very low contribution in a rainy month, it was found that the pump was not working properly, and this was then fixed. The recent total annual rainwater contribution was only 33% of the design target, as shown below. Causes were lower than average rainfall and pump failure for some of the period shown.
Treated water contributed only 48% of annual toilet flushing water demand, which was less than half of the target. It appears that too much water was directed to the irrigation system, causing an increase in the use of mains water. The cause was found to be a fault in the irrigation controller which was then fixed. The recent total annual treated water contribution was only 53% of the design target, as shown below. This is partly explained by the lower water volume to be treated which in turn meant that less treated water was available for use.
Overall, the average daily treated water volume was only 30% of the plant capacity and it seems that the grey water input was much less than expected, which was an interesting result in that it indicated that apartment occupants were using less water, a good outcome overall.
Total water used from all sources is shown below.
Overall use was comfortably under the design target value, which was a very good result.
The water use at this site was 109 L/day per person, which is 30% lower than the state government’s domestic mains then-target mains water use of of 155 L/day per person; a commendable result. Water from non-mains sources added 28 L/day per person bringing the overall usage of water up to 137 L/day per person.
Another worrying result came from the total energy (solar thermal plus natural gas) used for water heating. There are solar thermal meters installed that measure how much thermal energy is collected for the domestic hot water.
During the first three months of monitoring, a period of high sun exposure, the solar thermal contribution was only 3% of that expected.
Genesis Now investigated the poor performance of the solar water heating system, to establish causes. We found that the system was wrongly programmed, so that the solar pump was not operating when it should have. This issue was easily resolved with a program modification and the result was a drastic improvement in the solar contribution, which has reached 82% in the most recent 12 months, i.e. the solar water heating is contributing at least 27 times as much as it had before, despite lower average solar radiation. This represents a much better return on the same capital investment.
Still, a further improvement is considered to be possible and several options were suggested to the owner. These had not been implemented at the time of writing this case study, so we can’t report on results.
Notwithstanding this significant improvement, the overall gas consumption was nearly twice the target. Recent annual delivered energy was estimated at only 52% of gas energy with losses at 48% compared to the design assumption of 80% and 20% respectively. In the worst month, which occurred in Summer with low space heating, the estimated delivered heat was only 20%, meaning losses of 80%. These losses arose for several reasons, most notably due to the inefficiency of the water heaters and the system configuration which requires water heaters to serve both space heating and domestic hot water heating. Space heating is expected to be very seasonal from high in Winter to low in Summer, whereas domestic hot water heating needs are expected to be relatively constant and much lower than the Winter heating peak. Such an arrangement inevitably leads to water heating loads which are frequently much less than the lowest available from the installed water heater. Genesis Now monitored the water heater (“boiler”) operation, and found that the water heaters started frequently (up to several hundred starts per day) and operated for very short periods (1 minute or less) with this being most pronounced in Summer. Each start event is accompanied by a loss of heat due to safety purging of air in the heater, which overall became a large loss of gas due to the high number of starts.
The actual equipment and system configuration seem ineffective, but the costs for replacing it could be much higher that the gas savings. However, as the owner wanted this development to be a showcase and test-bed for future housing, there is value in trying to make significant improvements, even if they are not cost-effective at this particular site.
For electrical energy, the actual consumption was comfortably under the upper limit target and it appears that the photo-voltaic systems sometimes exceeded the owner’s consumption, so that there was a net export through the owner’s billing meter, resulting in a small financial benefit to the owner. As the owner was not being credited for this electricity export, Genesis Now recommended that the owner request this to be corrected.
D. GREENHOUSE GAS EMISSIONS
This housing development comfortably beat the design target for greenhouse gas emissions. This was in spite of much higher gas use (a lower emissions energy source), which was more than offset by lower electricity use (a high emissions energy source).
The owner is to be commended for setting targets for energy and water use and contributions from on-site systems, but the project did not include the systems and procedures which were required in order to measure actual performance, and facilitate early corrective in the event of poor performance. Genesis Now assisted in putting in place the missing metering and the collection, analysing and reporting of outcomes against targets, diagnosing the reasons for under-performance, and devising effective, cost-efficient rectification actions. While some shortcomings remain, generally performance has met or exceeded expectations.
The key messages are that without effective and reliable collection, analysis and reporting of utility data, you will never know whether a delivered project actually “delivers on the promise”. With the best will in the world both during design, construction and operation, always expect some glitches and, through a process such as described above, discover them as soon as possible and resolve them promptly by appropriate intervention.