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# Net Zero Energy Buildings and Low Carbon Emission, a Case of Study of Madagascar Island

By Modeste Kameni Nematchoua and Sigrid Reiter

Submitted: October 25th 2019Reviewed: December 13th 2019Published: March 25th 2020

DOI: 10.5772/intechopen.90854

## Abstract

### Table 1.

Thermal properties of some materials.

It was seen in this table that the materials as Hemp and Limestone Silicon do not produce CO2.

### 2.5. Description of software

The modeling of the building and all simulations were led thanks to Design Builder. The Design Builder software is one of the most famous existing software in modeling and optimization of the building. It also helps reduce the carbon content. The most recent version 6.3 is used in this study. The Design Builder tool also minimizes costs and hours of discomfort.

### 2.6. Calibration of model

To calibrate this model, we compared the different simulated and measured values of a building typically encountered in Madagascar [23], by calculating the linear correlation coefficient (R2) to analyze the margin of error. The literature shows that the error is negligible if the correlation coefficient obtained is around of ±1.

### 2.7. Wind turbine and photovoltaic systems

Wind turbine with alternating current worked 24/7. This wind turbine was a rotor type horizontal with a diameter estimated to 41 m, a height of 31 m, number of blades 3, with a maximum power coefficient of 0.4.

The photovoltaic panels occupied almost three-quarters of the roof area, making an angle of 45°C, with maximum orientation from south to north. The different panels consisted of polycrystalline cells with a mixed association.

### 2.8. Scenarios

In the reference scenario, we decided to study this residential building without any physical constraint. In its state as naturally as possible, and there is no source of electrical production. In this case, we use the A2 scenario, designed by the IPCC, which is the most realistic in Madagascar [24] for assessing indoor air quality and temperature in the future.

In a scenario 1, we install photovoltaic panels on two-thirds of the roof, while increasing the thickness of insulation by 2 cm (from 9 to 11 cm). The main facade is oriented from south to north, with solar protection on each window. The inclination of the solar panels is set at 45°C. The network was not connected to a power storage system (e.g., the battery).

In Scenario 2, we apply all the details presented in Scenario 1, except that the entire power grid is connected to a storage system. In addition to this, we apply the wind turbine to the building, whose characteristics are detailed in the previous paragraph. We made simulation this building according to each scenario and we got found new results.

## 3. Results and discussions

### 3.1. Indoor air

Air temperature and relative humidity are both environmental parameters which their variation has a significant impact on the occupant’s comfort. Figure 2 shows the variation of indoor air temperature in the new building. We can see that currently, in the building, indoor air temperature varies from 19.83 to 22.57°C; in 2030, the indoor air temperature is expected to be between 19.96 and 22.82°C; in 2050, in the same condition, indoor air temperature will be between 20.41 and 23.10°C. Globally, indoor air will increase to 0.30°C in 2030, and 0.52°C in 2050; compare to current air temperature. In addition, it is seen in Figure 3 that presently, relative humidity varies between 59.57 and 75.41%. In the future, it will vary between 58.77 and 76.03% in 2030, and, from 59.82 and 77.25% in 2050. The analysis showed that relative humidity will increase to 1.51% in 2030, and 2.73% in 2050; compare to 2017. The ASHRAE 55 ranges of comfort suggested indoor air temperature of 23–26°C; and relative humidity of 30–60% [25]. These different values are outside the ASHRAE ranges. Antananarivo is dominated by several mountains which affect the climate of this city. This interval is low compare to that found by Nematchoua et al. [26], in traditional buildings in Madagascar, which were between 24.6 and 28.4°C.

### 3.2. Electricity

Figure 4 analyzed the potential of total energy demand and produce by this building. Monthly electricity consumption varies between 123.8 and 137.1 kWh.

We can see under basic of this scenario electricity generated by this building corresponds net to electricity consumption; with zero cooling energy building during the different seasons. In the specific case of this scenario, which simply recommends an application of solar panels covering a total area of 182 m2, Net Zero Energy Building objectives are achieved for this building(energy produce = energy consumption). Electricity generated was estimated to be around of 0.49 kWh/m2. In the second scenario which some results are showed on Figure 5, it was applied simultaneously wind turbine and photovoltaic panel on the building.

It is noticed that in this case, the electricity generated by the building is equal to 13 times the average electricity consumed by the building. At this precise moment of operation of the building, the new building can be considered as a building with positive energy, that is to say it produces more than it consumes (energy consumption < energy produced). The annual total electricity that can be sold to individual consumers is estimated to 18946.86 kWh per year; it allows to save 4550\$. The frequency of comfort and total energy consumption is showed on Figure 6.

Discomfort potential was estimated to 71.2% (current); 74.4% (2030), and 76.8% (2050). These results show that in 2050, indoor air of the building will be 5.6% more uncomfortable than currently.

It is very important to notice that in specific case of scenario1, energy demand is found at zero. This does not mean that the building does not consume energy, it is just to explain that at this point the energy production is equal to the consumption of the building. The different energy values assigned a sign (−), explain that at this moment there is overproduction. These results are very interesting, and can be used by the building specialists. The electrification rate in Madagascar is one of the lowest in Africa: only 15% of the inhabitants are connected to an electricity grid. This figure rises to 58% in urban areas and drops to 4.7% in rural areas, which nevertheless accounts for 70% of the country’s population. It would be recommended to the Malagasy government to create favorable conditions to encourage the population to design new buildings more ecological and comfortable. One of the limitations of this research is that the type of building proposed costs up to 40% more expensive than the more conventional buildings found in the big island. But today, it is revealed in the literature that only 2% of the Malagasy population would be able to build this kind of building. We are well aware of this, but we think that the ideal for a more sustainable solution is to build new buildings in the big island by respecting the criteria mentioned in this study.

## 4. Conclusion

In this research, we analyzed and suggested a model allowing to reach net zero energy building and in certain measure created a building with positive energy in Antananarivo. Operational carbon was estimated to be around 3.7 kgCO2/m2. The operative temperature was between 19 and 23°C, in this period, the comfort potential was from 30%. The results found in this study showed it is possible to reach objective “Net Zero energy building” in Madagascar island by respecting the way detailed in this research. The degree of vulnerability in climate change is very high in Madagascar. The Malagasy government should propose more reliable control and adaptation strategies, for example the case of the extension of ecological buildings is very interesting. In a future study, we will study the case of implementation of the concept Net zero energy neighborhood.

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Modeste Kameni Nematchoua and Sigrid Reiter (March 25th 2020). Net Zero Energy Buildings and Low Carbon Emission, a Case of Study of Madagascar Island [Online First], IntechOpen, DOI: 10.5772/intechopen.90854. Available from:

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