Development of microscale wind maps for Phaluay Island, Thailand

AbstractPhaluay Island (9o 31’ 30.27” N 99o 41’ 19.66” E), located in the Gulf of Thailand, was selected by the Ministry of Energy of Thailand as a pilot model to demonstrate the development of a ‘Green Island’. Renewable energy including wind energy has been promoted as an energy resource for the island. In this study, a microscale wind map with a resolution of 90 m x 90 m was developed from a mesoscale wind data with the resolution of 3 x 3 km2 using Meteodyn WT wind resource assessment software. The results revealed the spatial variation of the microscale wind over the island. The high wind speed was found mostly in the mountainous area and finally the potential site for the installation of wind turbine on Phaluay Island was identified

Analysis of dryer performance for the improvement of small-scale litchi processing

Litchi is a significant cash crop in Thailand, but marketing is constrained by the perishable nature of the fruit. Drying can extend the shelf life of the fruit; however, in Thailand drying technology is still in its early stages of development. With the aim of improving locally available small-scale drying equipment, the performance of a litchi batch-dryer by a farmers' cooperative near Chiang Mai was studied. Drying conditions, energy consumption and product quality were monitored over three trials. Energy performance was analysed using instantaneous indices, leading to suggestions for possible design-modifications. About 29.8% of the heat input was used for moisture evaporation, 38.4% was lost via unsaturated exhaust air and 17.6% was lost to the ambient environment. An optimum air flow rate, one that minimises exhaust heat losses without increasing the drying time, was calculated. Temperature and air flow within the drying chamber varied, resulting in a non-uniform batch. To improve performance, a new design for the drying chamber air inlet is recommended

A Satellite-Based Sky Luminance Model for the Tropics

This paper presents a sky luminance model for the tropics. The model is mathematically expressed as a multiplication of two functions. These are , which is a function of the zenith angle of a sky element and solar zenith angle, and f, which is a function of the angle between the sky element and the sun. To obtain the analytical forms of these functions, the sky luminance data collected at Nakhon Pathom (13.82 ∘ N, 100.04 ∘ E), Thailand, during a four-year period were analyzed. Additionally, satellite-derived cloud index at the position of the sky luminance measurements during the same period was estimated. Based on values of the cloud index, the skies were classified into 10 types, from clear to overcast skies. By using appropriate grouping and mathematical operation of the sky luminance data, the values of the two functions were obtained and then fitted with empirical equations. The multiplication of these equations gives the final form of the sky luminance model. To validate the model, it was used to calculate the relative sky luminance at other three sites in the tropics. It was found that values of relative sky luminance calculated from the model and those obtained from the measurements were in reasonable agreement

Improved energy efficiency of farmers' cooperative litchi drying operation in Northern Thailand

In 2007, Hmong farmers growing litchi in the mountainous region of Northern Thailand started to dry the fruit in response to its declining market price. However, the locally available dryer, although affordable and of a size appropriate for smallholder farmers' cooperatives, showed excessive gas consumption, and this, along with rising fuel costs, imposed a threat to the drying operation. The objective of this study was to test low-cost, easy-to-implement modifications to a locally available convection dryer, to improve its energy efficiency. Experiments were conducted in cooperation with a Hmong farmers' cooperative in Northern Thailand. Insulation of the air ducts and control of the air recirculation rate led to energy cost savings of US$2.45 per dryer-load. With the modifications required being simple, the investment needed was recovered after only approximately 20 loads, while the energy efficiency of the dryer increased from 33% to 39%

Optimal physicochemical properties of dried litchis for Thai consumers

The litchi is a fruit essential for the economies of several Southeast Asian countries, but markets regularly reject it, mainly due to spoilage. Drying extends the shelf-life of litchis, but in Thailand the optimal characteristics of the dried product have not yet been determined. The purpose of this study was to determine the optimum physicochemical properties of dried litchis – those suitable for Thai consumers. The dried fruits were submitted to physicochemical measurement and consumer evaluation, with datasets subsequently integrated using circular ideal-point regression analysis. Response surface methodology was then used to predict the optimum physicochemical properties of the fruits. It was found that Thai consumer preferences with regard to dried litchis are for the fruits to be of golden-yellow color (L* ranging around 54; H ranging around 79°), to have a soft flesh (SMF ranging between 13 and 14 kN/100 g) and to have a sweet taste (TSS:TA ranging between 25 and 28). The results may be used in the future to prescribe pretreatments and drying conditions

Mapping Global Solar Radiation from Long-Term Satellite Data in the Tropics Using an Improved Model

This paper presents an improved model and its application for mapping global solar radiation from satellite data in the tropics. The model provides a more complete description of the absorption and scattering of solar radiation in the earth-atmosphere system as compared to the earlier models. The study is conducted in the tropical environment of Thailand. Digital data from the visible channel of GMS4, GMS5, GOES9, and MTSAT-1R satellites collected during a 15-year period (1995–2009) are used as a main input to the model. Satellite gray levels are converted into earth-atmospheric reflectivity and used to estimate the cloud effect. The absorption of solar radiation due to water vapour is computed from precipitable water derived from ambient temperature and relative humidity. The total ozone column data from TOMS/EP and OMI/AURA satellites are used to compute solar radiation absorption by ozone. The depletion of solar radiation due to aerosol is estimated from visibility data. In order to test its performance, the model is employed to calculate monthly average daily global solar radiation at 36 solar monitoring stations across the country. It is found that solar radiation calculated from the model and that obtained from the measurement are in good agreement, with a root mean square difference of 5.3% and a mean bias difference of 0.3%. The model is used to calculate the monthly average daily global solar radiation over the entire country, and results are displayed as monthly and yearly maps. These maps reveal that the geographical distribution of solar radiation in Thailand is strongly influenced by the tropical monsoons and local geographical features

Diffuse illuminance availability on horizontal and vertical surfaces at Madrid, Spain

The overall objective of this work is to provide diffuse illuminance availability at Madrid (Spain) through a statistical analysis of illuminance values corresponding to a long-term data series. The illuminance values are obtained from irradiance measurements by means of different empirical models for luminous efficacy. The values of diffuse illuminance on a horizontal and on vertical surfaces facing the four cardinal points are estimated and the different aspects related to daylight availability in an area with specific climatic conditions are analyzed. The experimental data consist of global and diffuse irradiance measurements on a horizontal surface provided by the National Meteorological Agency in Spain (AEMET) for Madrid. These data consist of hourly values measured in the period of 1980–2005. The statistical results derived correspond to a daylight typical year for the five surfaces considered. This information will be useful to building experts to estimate natural illumination availability when daylighting techniques are applied in building design with the main aim of electric energy savings

Characteristics of Different Systems for the Solar Drying of Crops

Solar dryers are used to enable the preservation of agricultural crops, food processing industries for dehydration of fruits and vegetables, fish and meat drying, dairy industries for production of milk powder, seasoning of wood and timber, textile industries for drying of textile materials. The fundamental concepts and contexts of their use to dry crops is discussed in the chapter. It is shown that solar drying is the outcome of complex interactions particular between the intensity and duration of solar energy, the prevailing ambient relative humidity and temperature, the characteristics of the particular crop and its pre-preparation and the design and operation of the solar dryer