Abstract

An electricity supply crisis has been faced by Indonesia. Applied long term electricity planning scenario by PLN was less considering environmental and new technology for utilizing renewable energies. Located under hot humid tropical climates, renewable energy sources in Indonesia can be found abundantly. While in use, buildings are intensive energy-users. Hence, poorly designed and operated contributes in the increasingly building energy consumption.

KEYWORDS: renewable energy, architecture, technology, building design

1. Introduction: electricity consumption and energy crisis

A good overview provided by The Energy Information Administration shows the status of electricity in Indonesia in 2004. Electrical-generating capacity has been installed in Indonesia estimated 21.4 GW, with the majority around 87.0% generated from non renewable thermal sources such as oil, coal and gas. The rest is from hydropower 10.5% and from geothermal 2.5%. Although, being the only member of OPEC in ASEAN, Indonesia ́s oil is predicted to be exhausted in the next 10-20 years. Total reserved oil in Indonesia is comprised of 5.2 billion barrels of proven and 4.6 billion barrels of potential reserves. With maintained production rate 0.54 billion barrels per year, the ratio between reserve and production is 18. It means the reserve oil could be used only within 18 years (Abdullah, 2005).

An electricity supply crisis has been faced by Indonesia. For people who live in Java-Madura- Bali, intermittent blackouts were issue monthly. Since around 60% of Indonesia ́s population lives in these three regions, approximately 57% of the 53% national electrification ratio generated by PLN (Indonesian Electricity State Company) is provided for them (Yoo, 2006). This problem should be urgently solved due to its influences in many aspects of human life. Unfortunately, long term electricity planning scenario by PLN still uses the conventional method in which only four factors are considered namely: population growth, demand-supply statistics, economics and private generation. The external influences such as environmental and new technology for utilizing renewable energies are not taken into account. By definition, renewable energy itself can be understood as the term used to describe a wide range of naturally occurring, replenishing energy sources (Omer, 2006).

2. Utilization of renewable energy

Located under hot humid tropical climates, renewable energy sources in Indonesia can be found abundantly. Very high daily solar radiation (about 4.8 kWh/m2) can be received in the country. Even it can reach up to 5.9 kWh/m2/day which was recorded in Waingapu on the island of Sumba. (Reinders et al., 1999).

Since all renewable energy sources have the origin in the sun, a high received solar radiation is beneficial on the potential of those energies. Unfortunately, this advantage is not much explored yet. From the summarized data in Table 1, one can observe that renewable energy resources utilization in Indonesia is still at the minimum level compared to their potential.

3. Building as important energy consumer

In Indonesia, electricity supply for industrial demand is growing the fastest. Anyhow, residential electricity is also increasing rapidly. According to Indonesian Statistic Bureau, in period 1995 – 2004, the residential sector accounted for 38% of total energy sales. Lee Schipper et al (1991) mentioned that this rapid growth of residential electricity consumption in Indonesia is caused by two factors: extension of electricity service to new homes and the rapid acquisition on home appliances.

In addition, buildings construction consumes a huge amount of resources. While in use, buildings are intensive energy-users. Hence, poorly designed and operated contributes in the increased building energy consumption. Some current significant issues of energy consumption in building are:

- Space conditioning To reduce indoor air temperature and adjust humidity to a comfortable level, air-conditioners grow rapidly in popularity in Indonesia since two decades. Hill (2002) mentioned that only 2% urban households in Indonesia installed air conditioner (AC) at their home. By comparison, this figure is relatively lower than other Asian countries. For instance in this case, 57.7% of Singaporeans posses’ air-conditioners when they are experiencing a nation transit from a developing country to a developed country status in 1998 [Wong 2004]. Since people live under hot humid tropical climates like Indonesian have perception that live in cooler environment better than their environment, AC is commonly set up below 20° C. Both window and split-type dominate residential air conditioning system due to their lower maintenance cost and individual controllability. Nevertheless, these systems have far lower efficiency than central water-cooled chiller.

- Illumination The large share of building energy consumption is taken by lighting. There is a custom to leave at least one light on all night for reason of security. Another reason is that Indonesian people prefer to sleep with the light on.

- Home appliances Important end-use of energy in residential sector are also for home appliances such as refrigerators, color televisions, rice cookers, irons, water pump and washing machines. In compare with other ASEAN countries, Hill (2002) listed Indonesia as the country with the lowest use of refrigerator with only 20% urban household.

4. The role of architecture in earth sustainability

The basic role of architecture is to create building as a human shelter. In general, it plays an important task to protect man against climate. Depend on climate characteristic where the building is located, habitability of buildings is keeping heat trapped inside such as in cold regions or protecting from high radiation effects such as in hot humid climate regions. In other words, architectural products are created for providing comfort in human living. Anyhow, the climatic consideration seems no longer taking into account in modern building today. Representing their modernity, most of buildings are clad in glass, inappropriately dark and require artificial lighting during the day. Although outside condition is pleasant, the room still needs air conditioning all year round due to improper applied building system. Why architects have been paid a little attention to building performance with respect to the climate condition? An interesting answer provided by Helena Coch (1998). There is a limitation to understand interaction between form and energy. Since energy is immaterial, so it is difficult for architects to imagine energy in their design. In contrast, artificial environment in building is much easier created than naturally one. It follows that applied building form is considered only on the basis of aesthetic and functionality.

Today, the role of architecture shift to other opposite position to protect climate against man. As mentioned in many publications (Omer, 2007; Müller, 2010), globally, buildings are responsible for approximately 40% of the total world annual energy consumption. At the same time, building sector also contribute to the environmental impact through its CO2 and NOx emmisions. To reduce this building energy consumption and its negative impact to the environment, promoting innovative renewable technologies is meaningful.

Renewable Energy Technologies

The development of technology can not be avoided in field of architecture. Combining structures, smart materials and climate can reduce primary energy consumption in building sector.

(1) Solar control and day lighting optimization The use of daylight and passive solar design have long been recognized as a potential energy efficient design strategy by reducing electrical demand and the associated sensible cooling load due to artificial lighting (Li & Wong, 2007). Energy is actually not saved by day lighting, but switching off or dimming down electrical lights especially during the daytime can decrease energy requirements for internal lighting and cooling. Many case studies on day lighting report energy savings of as much as 52% along the window wall (Leslie, 2003).

With a mainly direct sunlight climate, the principal objective of window design in tropics regions is to provide thermal comfort during hot season. Since the sky condition under hot humid climates is primarily bright and overcast, most traditional buildings are constructed with very wide awnings or verandas shading to protect building from the sun radiation. As a consequence, shaded windows can cause a minimal utilization of natural light in building even though illuminance levels are very high. By comparison, daylight factors inside building in the tropics are typically lower than commonly achieved in European or North American buildings (Edmonds & Greenup, 2002).

In tropical buildings, the primary concern is radiant heat control. The simplest and effective used method to control heat through window is external shading in various forms such as venetian blinds. Generally, conventional shading systems are employed to block direct sunlight using non- transparent materials to prevent overheating and glare. Unfortunately, it follows that visual task indoor is going to be reduced.

A potential energy efficient design strategy for building is daylighting. In typical Indonesian residential buildings, especially in single houses, all external walls are usually situated with one or many windows for ventilation and lighting. Anyhow, the expansion of residential building stock in Indonesia creates a dense-urban environment which restricts quantity of daylight into building due to limited free outdoor space or shading effect from nearby buildings. For this reason, innovative daylighting design such as roof monitor, light pipes, or laser cut panels can be explored to transport natural light from outside especially in building with a deep plan.

There are three principal of daylighting technologies method (Müller, 2010) which is also possible to be developed and applied in tropical region:

3) Combined solar shading and (redirection of sunlight)

Thermal and natural ventilation

Natural ventilation is a phenomenon of indoor air movement driven by wind and thermally (buoyancy) generated pressures (resulting in stack effect) (Liddament 2002). For harnessing these forces, thus the careful sizing and positioning of opening should be taken into account by building designers.

Today, designing naturally ventilated building is concerned with creating adequate and well distributed indoor airflow since thermal comfort and healthy indoor air quality have been becoming important issues. Ayad (1999) argued that good ventilation of building has positive effects on occupant ́ thermal comfort and indoor air quality. For this reason, obtaining speedy air velocity is always suggested by providing natural ventilation system under hot humid climates.

An invaluable method for buildings in hot humid region is the “cross ventilation” system. It refers to condition where a given space is connected by apertures to both pressure and suction areas of the interior (Givoni, 1976). This is designed by placing windward openings opposite to leeward openings. It follows that unimpeded airflow path between the incoming and outgoing airstreams can pass through the zone of occupancy. However, to keep this expression consistent, position of openings in relation to the wind should be taken into account since air motion can be caused by external wind even without cross ventilation. It can occur in one space with many openings which are facing zones at similar air pressure.

Thermal comfort in hot humid tropical climates depends not only on the rate of supplied fresh air into the room. It could be more dependent on the air speed across occupant ́s body which can promote cooling evaporation. To provide this task, solar chimney is one of useful passive method which can be utilized.

In this method, solar energy absorber is employed with open on top and bottom. It results in inducement of airflow through a building when solar radiation impinges on it. This operation can be explained in detail as follow: solar radiation which passes glazing is absorbed at wall surface. By convection and radiation, air in the chimney is then heated. It follows a decreasing of air density, which causes it rise. Afterward, from the attached room it will be replaced by air below. The rate of air, which is drawn through the room, is dictated by the buoyancy-force experienced.

A lot of Indische buildings in Indonesia are characterized by a fleche at the top of roof as shown in Fig 4. For creativity on architectonic view, this inspirational old system can be developed again in practice of architectural design today and the future. One can also see a good example of solar and wind chimney scheme in Fig 5. It influences not only on thermal performance but it may also create unique architectural feature. For application under tropical climates such as in Indonesia, modified roof typologies are needed to adapt the prevailing problem.

References

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