Miguel Ángel Martínez Bohórquez

A new approach to obtain I-V and P-V curves of photovoltaic modules by using DC-DC converters

The achievement of I-V and P-V curves of photovoltaic modules gives the possibility of obtaining their characteristic parameters: the short-circuit current (I/sub sc/), the open-circuit voltage (V/sub oc/), the maximum power point (MPP) and the fill factor (FF). These values are significant for the design of a photovoltaic system. These curves depend on the global irradiance (G), the temperature (T) and the spectral distribution of the solar irradiation. In this paper, a new methodology to determine the afore mentioned curves by using DC-DC converters is proposed. This methodology allows carrying out the complete sweep of the voltage and the current (including V/sub oc/ and I/sub sc/). Regarding the traditional methods, this new one provides the following advantages: a) minimum power loss with regard to the systems that operate in lineal zone (active zone); this implies several advantages in size and cost; and b) this new method allows an automatic adaptation of the interpolation interval.

A new application of the coupled-inductors SEPIC converter to obtain I-V and P-V curves of photovoltaic modules

The achievement of I-V and P-V curves of photovoltaic modules gives the possibility to obtain the exact operation point, the short-circuit current (Isc), the open-circuit voltage (Voc), the maximum power point (MPP) and the fill factor (FF). These are significant parameters for the design and for the start-up of a photovoltaic installation. In this paper, we propose and analyse by means of simulation the capacity of the SEPIC (single-ended primary inductance converter) structure to implement I-V and P-V curves tracers of photovoltaic modules, mainly because the SEPIC topology presents the capability of buck-boost conversion. Thanks to this property, a complete sweep of the voltage and the current given by a photovoltaic panel can be made, including Voc and Isc . This structure is implemented by coupled inductors and presents two fundamental advantages: 1) it allows to emulate a resistance at the input converter within the range [0,infin) and 2) it guarantees a null ripple in the input current when the magnetic coupling of his two inductors fulfils ZRC (zero ripple condition)

Ground Thermal Diffusivity Calculation by Direct Soil Temperature Measurement. Application to very Low Enthalpy Geothermal Energy Systems

This paper presents a methodology and instrumentation system for the indirect measurement of the thermal diffusivity of a soil at a given depth from measuring its temperature at that depth. The development has been carried out considering its application to the design and sizing of very low enthalpy geothermal energy (VLEGE) systems, but it can has many other applications, for example in construction, agriculture or biology. The methodology is simple and inexpensive because it can take advantage of the prescriptive geotechnical drilling prior to the construction of a house or building, to take at the same time temperature measurements that will allow get the actual temperature and ground thermal diffusivity to the depth of interest. The methodology and developed system have been tested and used in the design of a VLEGE facility for a chalet with basement at the outskirts of Huelva (a city in the southwest of Spain). Experimental results validate the proposed approach.

A New Metre for Cheap, Quick, Reliable and Simple Thermal Transmittance (U-Value) Measurements in Buildings

This paper deals with the thermal transmittance measurement focused on buildings and specifically in building energy retrofitting. Today, if many thermal transmittance measurements in a short time are needed, the current devices, based on the measurement of the heat flow through the wall, cannot carry out them, except if a great amount of devices are used at once along with intensive and tedious post-processing and analysis work. In this paper, from well-known physical laws, authors develop a methodology based on three temperatures measurements, which is implemented by a novel thermal transmittance metre. The paper shows its development step by step. As a result the developed device is modular, scalable, and fully wireless; it is capable of taking as many measurements at once as user needs. The developed system is compared working together on a same test to the currently used one based on heat flow. The results show that the developed metre allows carrying out thermal transmittance measurements in buildings in a cheap, quick, reliable and simple way.This paper deals with the thermal transmittance measurement focused on buildings and specifically in building energy retrofitting. Today, if many thermal transmittance measurements in a short time are needed, the current devices, based on the measurement of the heat flow through the wall, cannot carry out them, except if a great amount of devices are used at once along with intensive and tedious post-processing and analysis work. In this paper, from well-known physical laws, authors develop a methodology based on three temperatures measurements, which is implemented by a novel thermal transmittance metre. The paper shows its development step by step. As a result the developed device is modular, scalable, and fully wireless; it is capable of taking as many measurements at once as user needs. The developed system is compared working together on a same test to the currently used one based on heat flow. The results show that the developed metre allows carrying out thermal transmittance measurements in buildings in a cheap, quick, reliable and simple way.

A New Automatic System for Angular Measurement and Calibration in Radiometric Instruments

This paper puts forward the design, construction and testing of a new automatic system for angular-response measurement and calibration in radiometric instruments. Its main characteristics include precision, speed, resolution, noise immunity, easy programming and operation. The developed system calculates the cosine error of the radiometer under test by means of a virtual instrument, from the measures it takes and through a mathematical procedure, thus allowing correcting the radiometer with the aim of preventing cosine error in its measurements.

Method and Device for Measuring Characteristic Curves in Photovoltaic Systems

The invention relates to a measuring device that can capture the characteristic curves in photovoltaic systems, such as current versus voltage (I-V) and power versus voltage (P-V) of a solar cell (CS), of a photovoltaic panel (PV) or of a group of same. The invention is characterised in that it is formed by one or more DC/DC converters (10) [Direct Current/Direct Current], one or more solar cells (20) or photovoltaic panels (30), a capture and display device (40) and a control circuit (50) connected to the converters.

Energy Retrofitting and Social Housing Instrumentation Attending Passive Criteria. Case Study in Winter

This paper analyzes the conditions of interior comfort in passive houses in winter, depending on the daily variation of indoor air temperature under sealed envelope conditions. Shows, based on data obtained by real-time instrumentation of the rehabilitated housing, that is possible to achieve comfort conditions compatible with energy poverty situations in winter, without active cooling systems. Proposes the adaptation of passivhaus standard for energy rehabilitation of existing buildings, focusing actions on improving the quality and continuity of the thermal envelope, minimizing air infiltration and ensuring indoor air quality by installing an air ventilation system with double flow heat recovery.