Abstract

Abstract
The main objective of this paper is to present a study on the wind energy potential that is being developed in the Region of Tras-os-Montes and Alto Douro. This study started in July 1996 and will continue until the end of 1998. In order to have an adequate characterisation of the wind energy potential in this region it is necessary to measure the wind speed and direction in several places. At this moment the data are being collected at nine places. Due to lack of space, only four places will be addressed in this article. The Region of Douro and Alto Tras-os-Montes has an area of 12,235 km(2). It is located in the Northeast part of Portugal and represents 57.7% of the North Region. Other projects refer to this region as having great potential in the field of renewable energies [1,2]. From the analysis of the collected data, it seems that wind energy in Marao and Alvao mountains is one of the most interesting renewable energies [3,4].

Abstract
Psychrometer sensors are widely used for monitoring greenhouse air humidity because of its simplicity, low cost and accuracy. For proper operation the wick, which is immersed in a water reservoir, must maintain a continuous supply of water to the wet bulb temperature sensor. This implies the need to refill periodically the water reservoirs, which is the major limitation of these sensors. To avoid this problem an electronic psychrometric sensor was developed. A microcontroller is used to read the wet and dry bulbs temperatures and compute the vapor pressure and relative humidity. In addition, it controls a micro heat pump to supply continuously water to the reservoir.

Abstract
This paper presents an on-chip silicon bulk-micromachined Soil Moisture Sensor (SMS) for irrigation control in greenhouses. The system-on-a-chip includes the SMS, readout electronics, self-test, calibration facilities and a digital bus interface for external data transmission. Moreover, this low-cost device can be applied in several locations (e. g. per each plant root), and networked together with the 1-wire bus. The heat-pulse technique is used (for measuring the maximum temperature on a distant point) to determine the volumetric heat capacity and hence the water content of a porous media, such as soil. In order to validate this method, experimental results were achieved with a macrosensor based on the heat-pulse and capacitance methods. The capacitance method relates the volumetric water content with the capacitance change (dielectric properties) of a probe, inserted in the soil. Several tests were performed for different type of soils and water contents. These results are compared with the measurements achieved using the conventional thermogravimetric method.

Abstract
In the recent past, the distance between the sensing and processing points imposed critical constraints on the application of most PC-based data acquisition and control systems. Nowadays, it is possible to access the control systems installed in remote sites over the Internet. The World Wide Web has revolutionised the Internet by providing a medium for the dissemination of information, and the use of this technology can have a great impact on Agricultural Systems as well. These technologies allow almost any PC with a browser and a communication link to the Greenhouses to be used as an operator workstation, which gives benefits to the users who need remote access to greenhouses. Besides this, modern systems for agricultural applications are based on interconnection and integration of several Local Area Network (LAN) technologies combining data connectivity with user mobility. With a browser, the user is able to download a set of web pages, review information about the status of the system in real time, by running Java Applets, and display it in a browser window. Also, in this way it is possible to remotely configure any network node.

Abstract
Improvement of crop quality and yields is a demand in modern greenhouse production systems. Also, production costs must be kept as low as possible to guarantee market competitiveness. The achievement of these goals implies the use of complex management and control systems to regulate, in an efficient way, a large amount of interactive physical variables. Recent developments in hardware and software tools, namely microprocessors and microcontrollers, lead to the integration of complex control and management tasks in agricultural exploitations. In this paper is presented a data acquisition and control network that was implemented with the aim of being applied to any agricultural environment. The network has three main operating levels. At the lower level, a set of remote microcontroller stations perform data acquisition and radio frequency transmission to a collecting and control station. The control station, which generates actuating signals, is linked to a higher-level network based on PC's. The management and supervision of the entire greenhouse system is performed at this lever. Also, the results achieved with its application to the environmental control of a set of greenhouses located in the north of Portugal are described. The proposed architecture is now being installed in several commercial exploitations in order to evaluate its performance and introduce any improvements required by the growers. After this phase, the network will be available commercially through a joint Venture between UTAD University and a Portuguese greenhouse constructor.