Passive solar energy

At present, solar energy could be characterized as passive solar strategy and active solar strategy depending on the way they converted into another type of energy. The majority of passive solar design of buildings are based on the thermal mass which is a certain type of material that could store heat for some time. It is achieved by its high thermal resistance. This kind of strategy is suitable for countries with large temperature difference between day and night when it could block the overheating from sunshine in daytime and release the heat to inside room during the night (Figure 1).

                                Figure 1. Thermal mass in day and night in solar chimney 

Figure 2. Working process of solar chimney

In fact, the most famous passive solar strategy is known as solar chimney which could both be used in passive way or active way.  Basically, it is a wall with one side of glass which is positioned toward the Sun. And other sides of the wall are made of thermal mass. Normally, there are two vents in the wall between the inside room and the chimney. During the day, the two vents are open. The sunshine heats up the air inside the chimney. So the air inside the chimney should be warmer than the room air and it would rise vertically through the chimney to inside space based on buoyancy influence. And the cold air on the basement would keep adding into the chimney that induces an simple ventilation system for the whole building. In the night, the two vents would be closed in order to maintain heat in the building.

Figure 3. Passive solar lighting

The sunshine could also be used for lighting during the daytime directly. It is known as "Sun-Pipes" which is fully glazed and adjusted to suitable angle to let the light to coming into the room for lighting through reflecting. The pipes are normally installed on the roof that oriented to South, and the mirrors inside the pipes have a high reflecting capacity  which allows the natural daylight to access into the room deep inside the building.
In fact, passive solar strategy is the way of using solar energy without any kinds of mechanisms supplied or exported by electricity. Passive solar strategies would save a lot of energy for heating and lighting during the day. However, the drawbacks of them are represented to be obvious as they highly depends on the Climate.

Reference

ENERGY. GOV (2012). Passive Solar Home Design  [available online]<http://energy.gov/energysaver/articles/passive-solar-home-design>

ECO-WISE (2012). Passive Solar Design: Sustainable Sources-18 years of online Green Building information.  [available online]
<http://passivesolar.sustainablesources.com>


Alfredo Fernandez-Gonzalez  et al.(2012)  SIMPLICITY AND INTEGRATION: PASSIVE SOLAR DESIGN AND PASSIVE HOUSE  

IN INTEGRATED PRACTICE AND EDUCATION 

Planet Energy Solutions (2010) Passive solar lighting [available from]
<http://www.planetenergy.co.uk/Solar%20lighting%20information%20sheet.pdf>

Introduction

Globe fossil fuels consumption

At present, the primary energy (mainly the fossil fuels) shortage becomes a globe issue when it is the blood of development and civilization. In fact fossil fuels includes three parts: Coal, Petroleum and Natural gas that formed natural process such as anaerobic decomposition which would take millions of years. According to Energy Information Administration in 2007, fossil fuels account for 86.4% of the total primary energy consumption. And the world energy consumption would grow about 2.3% per year. It indicates that the reserves of fossil fuels are being depleted much faster than new one are being made. Some researches have proven that if the consumption rate of fossil fuels remains same until they are used up, there is enough oil to last 42 years, when there is enough natural gas to last 61 years and there is enough coal to last 133 years. Furthermore, the combustion of fossil fuels would emit huge amount of carbon dioxide which becomes one of the main causes of globe warming. So renewable energy which could be naturally replenished at a constant rate comes along to meet the abundant energy consumption in the future. And it is assumed to have less impact to the environment.
The blog would be divided into 5 parts that represents the 5 main types of renewable energy: Solar, Wind, Geothermal, Tidal and Biomass.
There is only one thing that should be considered is that, according to energy conservation, the energy would not disappear or exhausted. It could only be transmitted from one type of energy to another type. All of energy that used by human beings are end up with heat which could not be used. So in theory, the energy is infinite. However, we just have not found the best way to use it. 

Reference
^ "U.S. EIA International Energy Statistics Retrieved 2010-01-12.