School For Higher and Professional
Education (SHAPE) University of the West of England, Bristol
BEng (Hons) Building Services Engineering
UBLMN7-30-3 Low Carbon Building Services
Assessment 2-Energy Systems Report
Zero Carbon Building Services(ZCB)
Student Name : Leung Tsan Kit
Student number: 187260726
The ZCB is the first zero carbon building in Hong Kong. This project was jointly built by the Construction Industry Council and the Hong Kong Government. Also, ZCB is a green state in high-density cities. ZCB is enclosed an area of 14,700 square meters, including a 3-storey zero-carbon world building and a green area. Its main facilities include: Indoor exhibition and education venue, Green home, Green office, Green tea room, Multipurpose hall, Green square, Outdoor exhibition area and the Hong Kong’s first urban native forest. ZCB is emphasis on the coordination between natural bionetworks and buildings, with the primary goal of minimizing energy consumption and producing renewable energy (even more than needed). To attain the zero carbon emissions, ZCB has adopted an integrated design based on the energy ladder and green building benefits: Energy efficient design, Energy efficient green technology and systems, Efficient use of renewable energy, Low carbon building materials.
According to the ZCB, they are using two types of energy operations which are biodiesel tri-generation and solar energy panel had installed on the ZCB. The biodiesel tri-generation is using the waste oil for the major fuel sources. There are three functions for the generating that integrated system for refrigeration, heat generation and power generation to ZCB. On the other hand, solar energy is one of the most important and the most obvious feature in the building design. The solar energy is a renewable energy which can engage the solar energy and heat from the sun power to transfer electricity.
Bio-fuel is a renewable energy which is generated by biomass which likes the dead body of organic matter, fuel or other industrial raw materials. Moreover, bio-fuel also can be produced by different wastes which like manure, sewage, green waste, plant material, food waste etc. On the other hand, solid waste, liquid waste and gas also can produce bio-fuel. In the ZCB, there are using the liquid of bio-fuel. At the site, the biodiesel tank and the generator set are built on the ground floor and the underground of biodiesel tri-generation system are providing three types of energy for ZCB such as electric power, cooling load and heat in ZCB.
Transesterification of vegetable oils, animal fats or waste cooking oils is a process of traditional biodiesel. In the transesterification process, the glyceride is reacted with an alcohol (usually methanol or ethanol) in the presence of a catalyst to form a fatty acid alkyl ester and an alcohol. For that, waste cooking oil as a source of renewable energy to create electricity
There are a lot of ways to make biodiesel, one of the common in Hong Kong are using is the method is used to prepare biodiesel. This reaction is called a transesterification reaction and the process is carried out in four steps. The first step is to mix the alcohol with the catalyst, usually a strong base such as NaOH or KOH. The alcohol/catalyst is then reacted with a fatty acid to affect a transesterification reaction.
Solar energy panel:
ZCB’s main roof has a beveled design with a slope of 17 to 20 degrees, allowing the polycrystalline silicon photovoltaic panels mounted on the roof to receive more direct solar radiation for optimum performance.
Solar energy is a type of renewable energy source that comes from solar radiation, including light and heat. Since the solar panel (photovoltaic cell) will receive light energy and heat and transfer energy to the power source as ZCB. This is commonly used in Hong Kong, which is why solar energy can be easily absorbed from the sun. On the other hand, this is not only easy to collect, but solar energy can be collected inexhaustible. In Hong Kong, solar panels are common as building services. Therefore, ZCB uses solar panels above the roof and installs many types of solar panels. At ZCB, there is an instrument that records how much solar energy is collected through those PV (photovoltaic) panels in a year. The process by solar panel to convert lighting energy into electricity. First, solar panels are generating direct current (DC) rather than the alternating current (AC) that your utility company delivers. This means that the energy from a solar panel must be converted before it can drive the toaster. It also often must be stored: you may want toast when the sun isn’t up, and the solar panels don’t generate power in the dark.
This depends on how much light there is to convert, and there are other limitations to the process. The amount of energy they capture is dependent on the properties of the material absorbing the light, and the junction between the two materials. This combination will only absorb specific frequencies of light. Some modern solar panels get around this by including multiple materials and junctions between them (called multijunction cells) that can absorb different frequencies of light to capture more of the available energy.
And then we according to the EMSD, the solar is output the dc power, so we need to install the inverter, and then we need to install the insulation transformer to let the dc power to be ac power, finally it can pass to the meter or switch board.
As the type of using panel, there had 3 type of PV panel were installed on the roof of ZCB, such as cylindrical CIGS, multi-crystalline and BIPV-thin film panel.
With the rapid development of solar photovoltaic technology, many scientists have combined two different solar cells to make breakthroughs in solar energy conversion efficiency, so that different solar photovoltaic materials can be shortened and developed to their respective advantages. Among them, perovskite is one of the common combinations, and the technology has the advantages of low cost and easy manufacture and can also be made into a thin film solar panel. CIGS Solar is the most efficient conversion system for commercial thin-film solar cells. CIGS is a compound semiconductor of materials used in solar cells, and the light absorption range can range from 1.02 ev to 1.68 ev depending on the content of indium gallium. In the standard environment, the photoelectric conversion rate can reach 19.5%. If it is assisted by the concentrating device, the photoelectric conversion rate has reached 30%. If the flexible plastic substrate is used, the photoelectric conversion rate is up to 14%. Also, its cost and materials are also less than conventional silicon. The combination of the two will provide more solar panels for efficient flexible solar and building integrated solar energy. According to the CIGS information, CIGS’ existing coating technology, vacuum process technology can be divided into co-evaporation, salinization, sputtering (sputtering); non-vacuum process technology can be divided into coating process (Coating Process), electrodeposition (Electrodeposition), chemical spray heat Chemical Spray Pyrolysis.
CIGS thin film solar cell structure, the bottom layer is a substrate (Substrate), usually glass (Glass) or flexible metal (such as aluminum alloy foil, copper foil, etc.) and polyimide (PI), a layer of Mo back electrode is splashed on the substrate. It is mainly beneficial for conduction. The upper layer is the CIGS light absorbing layer, the upper layer is the semiconductor (CdS), which has a buffer function and can also help the electrons to conduct effectively. At the same time, the (i-ZnO) layer is mainly used to prevent the solar cell from being affected by the shunt phenomenon, thereby reducing the power generation process. The performance of the component. The upper layer is (AznO) as a transparent conductive layer. In addition to be the upper electrode, this layer must pass light to the CIGS. Finally, the light absorbing layer is plated with a metal aluminum wire. ZCB using the CIGS is going to tell us the advantages of CIGS thin-film solar cells: wide absorption range, large radiation intensity and angular flexibility, flexible, easy to large-area, low raw material cost.
The other one type of the PV panel is called BIPV, BIPV is a comprehensive building that replaces traditional building materials using photovoltaic materials and the building itself is becoming a huge source of energy without the need for external solar panels.
For design stage considerations, the optimal ratio of power generation to cost, skylights and facade is usually the largest appearance. Building electricity can supply some or all, existing buildings can be converted to BIPV buildings.
The biggest advantage is that the solar panel price can replace the original building materials and the installation cost is also considered to enter the building fortress, thereby reducing the cost of solar energy. Furthermore, in order to improve access speed and aesthetic factors, it is necessary to include solar energy in the design stage.
Finally, the last PV panel which his called multi-crystalline as polysilicon (p-Si) and multi-crystalline silicon (mc-Si). The process for making polysilicon is simpler and less expensive. The amount of waste cockroaches is small compared to single crystals. Also, Polycrystalline solar panels tend to be slightly less heat resistant than monocrystalline solar panels. This technically means that their performance at high temperatures is slightly inferior to that of monocrystalline solar panels. Heat can affect the performance of solar panels and shorten their life. But, Polycrystalline solar panels typically have efficiencies of 13-16%. Polycrystalline solar panels are not as efficient as monocrystalline solar panels due to their lower purity. Also, it reduces space efficiency. it usually need to cover a larger surface to output. We can see the multi-crystalline in ZCB as most of the PV penal is using multi-crystalline. The multi-crystalline speckled blue color.
Electricity Feedback into grid
Tri-generator can be found in ZCB. The three provided (ZCB) have many systems of power generations. The system can be independent. Due to good management, the use of the device does not require much use. Lighting with intelligent lighting management features saves energy. There are not many office air conditioners, and ZCB prefers to use the earth’s cooling and low-flow fans to provide wind. ZCB also has some energy saving modes. Continued use of the third generation will reduce greenhouse gas emissions by 8,250 tons, a 45% reduction in energy consumption compared to traditional buildings. Sometimes three generators produce too much power and ZCB cannot store it. They will provide more energy to the local grid. Through the production of renewable energy, the network provides energy recompense every year. It shows all products using renewable energy samples. Sometimes extra power comes from solar energy. Due to the use of renewable energy, operating waste will be lower than traditional power systems, such as reducing fuel use, reducing greenhouse gas emissions and non-polluting hazardous chemicals. These reasons indicate that efficacy is superior to outdated feeding systems.
Combine Cooling and Heating Power
CHP is a thermodynamically effective use of fuel. In separate power production, some of the energy must be discarded as waste heat, but in cogeneration, some of these thermal energy is put into service. The heat emitted by all thermal power plants during power generation can be released into the natural environment through cooling towers, flue gases or by other means. Conversely, cogeneration captures some or all of the by-products used for heating, or very close to the factory, or especially in Scandinavia and Eastern Europe, as hot water for heating in living areas, with a temperature range of about 80 To 130 ° C. This is also called “CHP” (combined heat and power district heating, abbreviated CHPDH). A small cogeneration plant is an example of decentralized power generation. The by-product heat at moderate temperatures (100-180 ° C, 212-356 ° F) can also be used in an adsorption chiller for cooling.
CHP is an industrial process technique that uses waste heat from power generation for industrial manufacturing or waste heat from industrial production to maximize energy utilization. In the first generation, since the efficiency of the traditional generator is only about 30%, up to 70% of the fuel energy is converted into useless heat, and the cogeneration of electricity and electricity can reuse 30% of the thermal energy in the industry to make the fuel reach 60% efficiency. The system uses the waste heat generated by various industrial machines in operation, which is equal to the additional electricity generated.
CHP is most effective when heat can be used in the field or very close; but when heat must travel a long distance, the overall efficiency is reduced: this requires highly insulated pipes that are expensive and inefficient; It is transmitted along relatively simple wires and can be transmitted over longer distances for the same energy loss. It illustrates that the deployment of CHP depends on whether the use of heat is concentrated near the heat engine. CHP is the most cost-effective way to reduce carbon emissions from heating systems in cold climates and is considered the most energy-efficient way to convert energy from fossil fuels or biomass to electricity. That’s meaning the factors that influence its operation is the distance of the electricity and the temperature.
The bio fuel input is (1217+1020)/ (1-0.16)
The overall CHP efficiency: (1217+1020)/2663.09 = 0.82
Heat output: 1217KW
Heat Recovery efficiency
=1217/2663 x (1-0.32) = 0.31
Electric output: 1020KW
Assume electric generator 95%
Electric generation= (1020/2663) x 100% = 38.3%
Mechanical efficiency of CHP unit
0.383x 0.95 = 36.38% efficiencies
According to the calculation, Tri-generation system efficiency for the system up to 75% more than Fossil fuel power generation only 40%.
As a combustion method, it is assumed that biotin and a chemical formula are used. Moreover, the combustion process also produces air. In addition, combustion requires heat, water, fuel and oxygen to operate the system, so when oxygen is burned, the reaction is mainly water, carbon dioxide. The left and right sides are the same, but the performance is different. We must calculate each product that can be used as a fuel element. This helps us easily find the efficiency of the product. Volume analysis will show how many of these three elements and the results will affect combustion.
One of the best active system designs is call high temperature cooling system. The high temperature cooling system does not require excessive cooling of the air to achieve a comfortable humidity level, thereby saving air conditioning energy. This is primarily achieved by a separate cooling and humidity removal system. ZCB’s high temperature cooling system consists of chilled beams, underfloor replacement cooling and desiccant dehumidification. The chilled beam is an air conditioning system used to cool buildings. The water pipe passes through a “BEAM” (heat exchanger) that is suspended a short distance from the ceiling of the room. As the beam cools the surrounding air, the air becomes denser and falls to the floor. It moves up through the warmer air, resulting in constant air flow and room cooling. Underground drainage cooling is an air distribution strategy for providing ventilation and space adjustment in a building. The system uses an underfloor ventilation system below the raised floor to provide the conditioned air directly to the occupied area via a floor diffuser. The desiccant dehumidifier uses chemicals to remove moisture from the air. The desiccant dehumidifier works by passing a high relative humidity air through a desiccant such as silicone that absorbs moisture. The low relative humidity air stream is then refluxed over the desiccant to remove water molecules from the desiccant. In a conventional system, cooling and dehumidification are simultaneously performed. At ZCB, desiccant dehumidification is a separate process compared to combined cooling and dehumidification systems to increase efficiency. Cooling and drying air is supplied from the floor – it collects heat from the occupants and begins to rise. Vertical flow occurs near each passenger, resulting in a healthier environment because bacteria are less likely to spread and discharge stale air near the ceiling.
There are one of the best designs in the passive system which is called Light Pipes. Since there are some of the building in Hong Kong is using now, it is special in the ZCB site. The light pipes is using the daylight is collected through the dome of the building and then introduced into the room through a highly reflective inner channel. Also, the Light Pipes is only for daylighting, it avoids glare and does not consumes electricity. Also, Light Pipes mainly solves the problem of daytime lighting, it does not need any power energy, directly uses natural light illumination, there is no energy conversion, there is no electromagnetic wave radiation, and all parts of the product can be recycled and reused. Its light guide lighting products are energy-saving, Healthy, green products.
Light Pipes completely filters out the harmful infrared rays in the sun. The insulation is also very good, no matter how strong the sun, it can be converted into soft light, and it can also be adjusted by the switch. Replacing the light with natural sunlight is not only low-carbon, but also good for your health.
Light Pipes have large attenuation over long distances. The transmission of light in a Light Pipes lighting system is performed by different optical transmission devices. However, regardless of the transmission device, the efficiency of optical transmission is significantly reduced as the optical transmission distance increases. Even with a non-metallic light pipe that is expensive and has a small light attenuation rate or a multi-layered film, the transmission efficiency is reduced to less than 10% after 1 000 m. Also, the change of weather is an irresistible natural factor, if the weather are bad, it is a big effect for the efficiency of the light pipes.