cRRescendo Newsletter 31th of oct 2012

Datamonitoring in Almere

The monitoring in Almere aimed at administering the community level benefits of integrating renewable energy sources (RES) together with energy efficiency (EE) techniques that was demonstrated in two sustainable communities: "Noorderplassen-west" and "Columbuskwartier" as part of the cRRescendo-project within the European Concerto-program. The monitoring is followed by an in depth research that focused on establishing a good image of the energy-use of both areas.

The monitoring in two districts covered a large area and numerous parameters. Noorderplassen-west is the largest community with about 1500 dwellings while Columbuskwartier has about 700 dwellings. Communities have different RES and EE strategies and a unique development process. The aim was "to produce well monitored field experience of energy supply and demand patterns" as stated in the CONCERTO-program. The monitoring plan in Almere used multiple data sources at various levels. The data sources of monitoring range from manual recording (for large numbers of dwellings) to automated reading (for high frequencies of data collection). Data frequencies vary from yearly (for most dwellings) to each 5 minutes (for the Solar Island). Weather data required for normalisation is obtained from nearby official weather stations. Also characteristics of the buildings and the number of occupants are collected in order to obtain specific energy-uses. All data is stored in a dedicated database which provides a common framework for data filtration, corrections, inter- or extrapolation and timestamp.

The monitoring focused on the energy performance of communities at different segments of energy cycle: generation of energy, distribution of energy and energy demand or energy use. The three main subjects of monitoring of energy efficient communities are reflected in the analysis of:

  • Renewable energy supply
  • Rational Use of Energy
  • Eco buildings
Renewable energy supply
Generation of energy from renewable sources comes from the Solar Island in "Noorderplassen-west" and extensive use of solar PV-panels on buildings in CK.

The Solar Island, a large field of 520 coupled solar collectors with a total aperture area of 7135 m2, supplies renewable heat to the primary grid of the district heating of Almere. The flow of energy in Solar Island was measured from May 2010 to June 2011 in two ways: detailed (based on control-sensors of the system) and monthly (based on the measured heat delivered to the primary grid). The results indicate that the Solar Island converts annually 32% of the energy received as solar irradiation to heat. The annual share of solar energy is 57-61% for Almere and 34-38% for Noorderplassen-west itself within a range based on the measurement errors. The Solar Island produces 1.18-1.25 GJ/m2 which is comparable with individual solar collectors. The virtual unlimited storage capability of the district heating network, allowing more transfer of solar energy, is countered by the necessity to raise the temperature first to 70oC in the solar collector before it can contribute to the district heating which operates at a return temperature of 65oC.
Buildings in Columbuskwartier are equipped with stand alone PV-systems that meet (partially) the electricity demand of households. A large number of small PV-systems are installed. Most of the systems are CIS-technology and have a size of 1050¬†WP. The PV-systems are integrated in the roof (with various tilt and orientation) or in the façade. About 80 systems are monitored. The annual, monitored yield is 60-65 kWh/m2 PV. Most of the electricity (>95%) was used by the occupants themselves. The monitoring revealed various structural and non-structural defects of the systems causing loss of renewable electricity production. According to a detailed calculation based on applied PV- and inverter-technology, the actual yield is only 70% of the theoretical yield.

Eco buildings
The ECO buildings mainly consist of energy efficient dwellings in three performance levels: Eco-Houses, Solar Houses and Passive Houses. Each performance level was aimed both for single and multifamily dwellings. The number of multifamily buildings in both communities is low and so is the number of monitored multifamily dwellings. Therefore the analysis of the energy-use focuses on single family dwellings. The monitoring is carried out over a period of 24 months. The results for space heating, domestic hot water and electricity use are analysed and presented by category.

Domestic hot water use is important for accurate analysis but it is hardly measured due to the lack of separate meters. So, it had to be estimated in most cases. Dutch standard NEN 7120 was used in which the number of occupants is derived from the (usable) floor area of the dwelling. However an analysis of the actual relation between floor area and number of occupants differed significantly from the standard, especially for small houses (as is the case in Columbuskwartier). The observed relation between the number of occupants and the (usable) floor area of the dwellings is determined for both communities and used for the analysis of domestic hot water.

The number of people participating to monitoring activities through the internet varied each month. Sufficient amount of data are still achieved by using different sources for monitoring. In the end about 30% of dwellings were included in the monitoring with an active approach where households were visited by trained people once a year to gather their meter readings for three consecutive years. The yearly consumption data is interpolated to monthly values when required for the analysis. The interpolation and normalization depends on actual heating degree days . All ECO buildings are characterized with ambitious energy performance targets. The size of the dwelling determines strongly the heat demand and the electricity use. The actual constructed floor areas are significantly bigger for Eco Houses and Solar Houses compared to the cRRescendo-proposal. A similar observation can be done with respect to geographical location. Monitored houses in Noorderplassen-west have an average floor area of 178 m2 while houses in Columbuskwartier have an average floor area of 137 m2.

Tabel 1 - Average floor area of Eco-buildings (single family dwellings) according to the cRRescendo-proposal and the actual commissioned values.

The effect of building size can be seen in the next graphs and tables. While Eco Houses demand less space heating per unit floor area then expected, the total demand for space heating is the same as expected. The same is true for Solar Houses and Passive Houses with the additional remark that Passive Houses are constructed smaller then expected. Another observation is that Solar Houses use more space heating then expected per unit floor area as well as in total. This would also be the case if Passive Houses were constructed bigger. The higher the ambition, the harder it is to reach it. More attention is required for the construction process and for the use of the building by the occupants in order to benefit from the potential energy efficiency. Data collected monthly which requires a bigger effort from the occupants, is lower for Eco Houses as well as for Solar Houses. It is anticipated that people who volunteered to this kind of data collection are more conscious about their energy consumption. Hence it is possible that the data may not represent the average user behaviour. The differences in heat demand per m2 reflect the energy performance (coefficients) for the different categories.

Figure 1 - Average annual energy demand for space heating per square meter of floor area for all building types. The mentioned areas are proposed and commissioned values. (internet: monthly measurements, interview: yearly measurements)

Figure 2 - Average annual energy demand for space heating per dwelling for all building types. The mentioned areas are proposed and commissioned values. (internet: monthly measurements, interview: yearly measurements)

Electricity consumption is measured by three different monitoring methods; monthly (with internet), yearly (with interview) and detailed (with data-loggers) data collection. The variation in proposed and monitored consumption (see Table 2) can be explained by the difference of proposed and actual average floor area. There is a strong correlation between area and electricity demand for all types of energy efficient buildings. Moreover, the hourly data collection in 20 dwellings is used to examine electricity consumption patterns. Three distinct groups of consumers are created according to electricity consumption levels; low, mid and high electricity consumption. A similar weekly consumption pattern is observed in all groups, with peaks in the morning and afternoon, and a base load of approximately 50% of the average power consumption. The fluctuation of the energy consumption between highest and lowest thresholds is inversely proportional with the level of average consumption. The low average electricity consumers have the most extreme thresholds for consumption where as the fluctuation pattern is less fluctuating for consumers with a high electricity consumption (see Figure 3). The electricity consumption pattern and the groups are likely to represent certain occupancy types; the group with a low consumption being occupants that are not in the house during the day (office hours), the group with a high consumption being the occupants that display mostly in the evening electricity requiring activities.

Table 2 - Average energy demand for electricity in single family dwellings (kWh/year/building).

Figure 3 - Normalized average weekly electricity consumption patterns in Almere for different groups of electricity consumption (low, medium, high).

Rational Use of Energy
The rational supply of heat by the Combined Heat and Power station of Diemen was not operative until the mid of 2012. Therefore, the monitoring is limited to the assessment of the distribution losses in the secondary grid of the district heating system, e.g. the piping network between substations and the buildings themselves. This last part of the district heating system causes the largest distribution losses due to increasing branching of pipes. Supplied heat from several substations was compared with (extrapolated) heat demand from the connected buildings. As the energy demand is mostly monitored for dwellings, only some substations with only dwellings connected were analysed.

Table 3 - Monthly average heat demand and distribution loss per m2 floor area related to various substations.

The distribution losses vary from 30% to 100% of the actual total heat demand (space heating and DHW) depending on the substation and the period. It can be seen that with the exception of ABX 3 WR 2 the ratio of heat loss is inversely proportional with the energy performance of the buildings. The newly developed areas tend to have higher distribution loss ratios as a result of higher energy efficiency of dwellings (less heat demand). The excessive distribution loss is primarily related to space heating.

The monitored distribution loss is also compared with the theoretical distribution loss based on the Dutch standard NEN 7125. On average the difference of the total annual distribution loss between the two methods is 16.5 kWh/m2 or 20% of the total heat demand for substation ABX 3 WR 1. Possible causes are: higher operating set-points, missing heat losses (e.g. transmission loss of the substation-building), difference between the actual average heat demand and the monitored heat demand (e.g. actual average heat demand of all dwellings is higher then the monitored heat demand at 25% of all dwellings). However the observed extra heat loss could not be fully explained by these causes.. Some further investigation revealed a correlation with precipitation, evaporation and drainage in the area. Although the real cause could not be determined, the observed monthly effective insulation value of the piping system that would cause the extra distribution loss can be explained up to 50% (R2-value) by the accumulated precipitation in the ground. The owner of the district heating system also looked into the issue. Unfortunately the results of this additional investigation were not available at the due date of this report.

 



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