Desarrollo de prototipos de calefactores a gas hogareños de alta eficiencia

En este trabajo se pretende modelar y diseñar prototipos innovadores de calefactores de gas de tiro balanceado hogareños que tengan mejores eficiencias que los actuales disponibles en el mercado. Los nuevos modelos se crearán sobre la base de calefactores comerciales actuales, y con procesos de modificación accesibles a un usuario y/o técnico regular, y con costos moderados a bajos (menos de $50 por equipo). En un proyecto previo de los autores recientemente completado se cumplieron similares objetivos sobre un único modelos comercial de gran difusión (Emege línea patagónica) estudiado. Se observaron eficiencias de regulares a pobres, del 40 al 60$25 en producción en serie, se construyeron nuevos prototipos que alcanzaron eficiencias del 75 al 85%. El estudio anterior ha dado origen a logros científicos, plasmados en la publicación de 2 trabajos en Revista Nacional con referato, 2 más enviados a Energy Building (en evaluación) y 3 presentaciones en congresos internacionales con referato, acompañados de logros tecnológicos, plasmados en 2 solicitudes de patente de invención presentadas por el Conicet, y una conferencia ante todos los fabricantes nacionales brindada en el auditórium del Conicet, auspiciada por éste y la SeCyT. Todo esto fue realizado durante el 2006 contando con un subsidio de $15,000 de la SeCyT- Programas Especiales. Sobre la base de este trabajo anterior se enfocará el trabajo presente en desarrollar herramientas de cálculo que modelen los mecanismos preponderantes de transferencia de calor al ambiente. Estas herramientas permitirán estimar a priori el beneficio de distintas opciones posibles (por ejemplo: si conviene ensanchar la cámara de combustión o aumentar su altura), con vistas a su implementación práctica y validación experimental posterior. Estos modelos se transformarán así en una herramienta poderosa de diseño de nuevos calefactores, que permitiría a los fabricantes rediseñar un calefactor y evaluar su desempeño desde el tablero de dibujo, sumando criterios técnicos e interactuando con otros criterios (marketing, ventas, precio, etc.) igualmente importantes a la hora de decidir cómo será el nuevo producto, y han sido requeridas por el sector manufacturero. De nuestra interacción personal con varios fabricantes nacionales, y del estudio preliminar de sus modelos comerciales actuales, surge como evidente que la ausencia total de criterios técnicos con base científica y que permitan cuantificar las mejoras, como los que se pretenden desarrollar aquí, ha sido el factor causante de los pobrísimos diseños (desde el punto de vista térmico-aerodinámico) resultantes, que hoy podemos observar instalados en casi cualquier punto del país.n this work is intended: 1) to study experimentally the thermal efficiency of commercial appliances gas heaters for household space heating; 2) to modeling the thermal transfer mechanisms involved in this kind of appliances, in order to 3) developing a useful theoretical tool for assistant its design, and 4) to developing a new technical standard for the efficiency experimental determination. In our previous work similar objectives are been satisfied for a commercial gas heater (the EMEGE Patagonian series one). We have found that the actual efficiency is poor, between 40 and 60$25. This initial studied has give remarkable scientific achievements, like: 2 articles in scientific journal with referee (and 2 more been evaluating now), 3 presentations in international congress with referee. Also this study gives us many technological achievements, like: 2 invention patents claimed by Conicet and 1 conference to the national gas appliances manufacturers, supported by the Conicet and the SeCyT organizations

World Energy Saving from Cars: An Innovative and Feasible Proposal

Many devices have been proposed for energy saving (by heating water) from the waste heat of car engines, some dating as far back as the early 1900's. However, so what this heated water could be used for remains an open question. In this paper, a new proposal is presented to answer this question. This is an onboard car and on-ground systems, for heating water to be used for the benefit of the community, as this hot water would be applied to meet the heating demand in buildings. Concerns about the added mass on the car, costs, and benefits and the user interface were discussed, and a universal system that could satisfy all of these criteria was developed

Efficient heating of sanitary water with heat pump

This work presents a thermal and economical assessment about replacing the conventional household water heater (electrical, 100 % efficiency) by a modern heat pump water heater, which efficiency is proportional to the outdoor temperature, but about three and five times higher than the previous one. Thus, the efficiency calculated for capitals of Latin-American countries has obtained average values ranging from 298 % to 434 %. However, the payback period obtained is also related to the electricity tariff and the temperature of the cold-water grid, which varies from 0.064 US$/kWh in Paraguay to 0.233 US$/kWh in Costa Rica, and from 10 °C (La Paz) to 26.8 °C (Costa Rica). Thus, a ranking of payback period (replacing/new installation) was performed for an average consumption of a five-person family, obtaining values ranging from 2.4/1.4 years (Montevideo) to 10.5/6.1 years (Asunción), and also it was calculated the energy annual saving obtaining from 1,436 kWh (Costa Rica) to 2,660 kWh (La Paz). Thus, we have found great potential for household energy saving in Latin-American countries by substituting the conventional water heater by a modern heat pump.Se presenta un análisis térmico-económico sobre la sustitución del termotanque hogareño convencional por una bomba de calor, cuya eficiencia es varias veces mayor. Así, la eficiencia promedio calculada en las capitales de países latinoamericanos varía del 298% al 434%. Sin embargo, y como será analizado, el período de repago obtenido depende también de la tarifa eléctrica y de la temperatura del agua fría de red, yendo desde 0.064 US$/kWh (Paraguay) hasta 0.233 US$/kWh (Costa Rica), y desde 10 °C (La Paz) hasta 26.8 °C (Costa Rica). Para una familia promedio de 5 personas se calculó un ranking (recambio/nuevo) con períodos de repago que van de 2.4/1.4 años (Montevideo) a 10.5/6,1 años (Asunción); además, se calculó el ahorro anual de energía, desde 1,436 kWh (Costa Rica) hasta 2,660 kWh (La Paz). Así, hemos encontrado un gran potencial de ahorro energético en los hogares de los países latinoamericanos al sustituir el calentador de agua convencional por una bomba de calor

Desarrollo de techos de transmitancia solar configurable

Se presenta el desarrollo experimental y su evaluación térmica modelada para condiciones del desierto patagónico-pampeano, de un original diseño de techo o sobretecho de transmitancia solar configurable. Siendo un sistema de construcción simple y mediante el empleo de materiales convencionales de construcción, podría ser replicado rápidamente sobre cualquier techo sin requerir mano de obra especializada. Aplicado como sobretecho o toldo en viviendas unifamiliares, este sistema configurable podría reducir apreciablemente la necesidad de refrigeración estival y de calefacción invernal. En el modo verano, el toldo (constituido por una placa de policarbonato alveolar transparente) se llena de un líquido opaco o reflectivo, para minimizar la carga térmica solar sobre el techado, mientras que en el modo invernal se vacía del líquido para constituirse entonces en un toldo transparente de gran ganancia solar (por efecto invernadero) y de buena capacidad aislante térmico.The thermal modeling, developing of first prototype and experimental characterization of an innovative awning with configurable solar gain is presented. Being this an easy-made awning by means of standard building materials, this system could be universally mounted onto every roof by end-users. This configurable awning could avoid the requirement of air conditioning cooling system during summers, and reduce noticeably the space heating systems during winters. During summers, the awning (based in an alveolar polycarbonate sheet) mounted over roof is filled with an opaque &reflective liquid in order to blockage solar irradiation, and so, minimizing the heat load. During winters the liquid is drained, and the awning becomes a transparent greenhouse heating the roof, and providing additional thermal insulation too. The feasibility of this innovative concept for sustainable architecture was tested, and its economical impact was surveyed.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Desarrollo de techos de transmitancia solar configurable

Se presenta el desarrollo experimental y su evaluación térmica modelada para condiciones del desierto patagónico-pampeano, de un original diseño de techo o sobretecho de transmitancia solar configurable. Siendo un sistema de construcción simple y mediante el empleo de materiales convencionales de construcción, podría ser replicado rápidamente sobre cualquier techo sin requerir mano de obra especializada. Aplicado como sobretecho o toldo en viviendas unifamiliares, este sistema configurable podría reducir apreciablemente la necesidad de refrigeración estival y de calefacción invernal. En el modo verano, el toldo (constituido por una placa de policarbonato alveolar transparente) se llena de un líquido opaco o reflectivo, para minimizar la carga térmica solar sobre el techado, mientras que en el modo invernal se vacía del líquido para constituirse entonces en un toldo transparente de gran ganancia solar (por efecto invernadero) y de buena capacidad aislante térmico.The thermal modeling, developing of first prototype and experimental characterization of an innovative awning with configurable solar gain is presented. Being this an easy-made awning by means of standard building materials, this system could be universally mounted onto every roof by end-users. This configurable awning could avoid the requirement of air conditioning cooling system during summers, and reduce noticeably the space heating systems during winters. During summers, the awning (based in an alveolar polycarbonate sheet) mounted over roof is filled with an opaque &reflective liquid in order to blockage solar irradiation, and so, minimizing the heat load. During winters the liquid is drained, and the awning becomes a transparent greenhouse heating the roof, and providing additional thermal insulation too. The feasibility of this innovative concept for sustainable architecture was tested, and its economical impact was surveyed.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Propuesta de material multicapa aislante de bajo costo e impacto ambiental

El objetivo de este trabajo es mostrar las ventajas térmicas, ambientales y económicas, de un nuevo material compuesto propuesto para aislación térmica en viviendas. Se propone un sobre muro exterior que intercala varias cámaras de aire y capas de aislantes de baja emisividad infrarroja. Se desarrolla un modelo de resistencias térmicas unidimensional para calcular la transferencia de calor multimodal involucrada (conducción, convección y radiación), la cual se resuelve mediante iteración numérica. Como ejemplo, empleando 5cm de EPS (telgopor) en multicapas de 1 cm y cámaras de aire de 2cm, se obtiene una resistencia térmica similar a una capa sólida de EPS de 10 cm, dando un coeficiente global de transmisión de 0,346 W/m2°K. Se compara también la energía y los gases de efecto invernadero en la fabricación y el transporte del EPS, y se evalúan sus costos y aspectos constructivos.The aim of this work is to demonstrate the thermal, economical and environmental advantages of a new thermal insulation design to improve dwellings’ efficiency. An array consisting of several layers of air chambers separated by an insulation material of low infrared emissivity is proposed. The multimodal heat transfer (conduction, convection and radiation) is modeled by unidirectional thermal resistances, solving the coupled equations by numerical iteration. As an example, the calculations for an array with five layers of EPS of 1 cm thickness separated by 2cmwide air chambers are developed. The result is a global thermal transmittance value of 0,346 W/m2ºK, which is similar to the one obtained by a solid EPS insulation of 10 cm thickness. The energy used and the greenhouse gases emitted in the manufacturing and transport of the materials are also studied, as well as the cost of the alternatives and the installation possibilities.Tema 9: Nuevas Tecnologías.Facultad de Arquitectura y Urbanism

Holistic and Affordable Approach to Supporting the Sustainability of Family Houses in Cold Climates by Using Many Vacuum-Tube Solar Collectors and Small Water Tank to Provide the Sanitary Hot Water, Space Heating, Greenhouse, and Swimming Poole Heating De

This work presents a new proposal for supporting the sustainability of a single-family house in very cold climates by installing many vacuum-tube solar collectors and a small water tank in order to fulfill the whole dweller demands of heat: space heating, sanitary hot water, and warming both, a greenhouse (spring and autumn) and a swimming pool (summer). This way is obtained a sustained demand that maximizes the utilization of heat from solar collectors throughout the year. This system is designed intending to use the smallest tank that fulfills the winter heating demand, supported by vacuum-tube solar collectors and a little help from electrical heaters working just on the valley tariff. This innovative design gets the most sustainable (but affordable) solution. This goal can be achieved by using a small well-insulated overheated aboveground water tank, instead of the huge underground reservoir of heat used by most projects tested up today. These large communal projects use huge reservoirs to provide seasonal thermal storage (STES) capacity, but their costs are huge too. Besides, it was observed that all these huge STES suffer large heat losses (about 40%), due to constraints for thermally insulating such very heavy systems. On the contrary, our small aboveground water tank can be thermally insulated very well and gets affordable costs. In this work is developed dynamical solar-thermal modeling for studying this novel approach and are discussed its major differences with traditional design. This modeling is used to study the whole demands of heat for one family living in the same conditions of the Okotoks’ project. The Okotoks’ project is based on many flat solar collectors (2,290 m2) and a huge (2,800 m3) rocky-underground STES system in order to almost fulfill (97%) the space heating demand of 52 houses (15,795 kWh/y ea.) in Alberta (Canada), having an overall cost of 9 MU$(173,000 U$ ea.). We have already shown in previous work that this new proposal could reach noticeably lower costs (€30,500) than the Okotoks’ project in order to provide the same heating demand, by taking advantage of using 18 vacuum-tube collectors (solar area 37 m2) and a small (72 m3) well-insulated (heat losses 18%) water tank heated up to 85°C, which is the same temperature used in Okotoks and other traditional projects. Now, this proposal is enhanced by using a holistic approach to include other low-temperature demands (sanitary hot water and warming a greenhouse and swimming pool) that enhance the sustainability of dweller living. This way, the full production of heat from solar collectors is utilized (about six times larger than the single space heating demand, but using only 20 vacuum-tube solar collectors (21 m2 solar area) and a very small (10m3) water tank, reaching about a lower overall cost (€20,000), and so, the economic performance is enhanced as well. Besides, it is shown that using a small fraction of electrical heaters as a backup system (2%) and slightly overheating the water (up to 120°C@2 bar), which is feasible by using commercial stainless steel water tanks designed for such purposes, its economic performance could be again noticeably enhanced (reducing the overall cost to €20,000, and getting payback period less than two years). This way here is demonstrated the overall solar-STES system can be reduced by about half size meanwhile the energy output can be increased up to seven times. Hence, the thermal analysis performed suggested us strongly critic the traditional approach of using flat solar collectors instead of vacuum-tube collectors. This analysis shows that this choice has strongly driven the selection of a huge STES, which in turn increases noticeably the overall costs of the system since for such huge STES is mandatory to use underground reservoirs. However, this analysis also shows that without including those secondary demands, this proposal achieves a modest economic performance (payback period about 11 years) regarding its lower energy saved and compared against the “most smart” standard solution (one water tank with electrical heaters, costing about 5,000 U$ and exploiting the valley tariff of nocturnal electricity costing 0.1 €/kWh). On the contrary, when these secondary demands are included, the payback period is reduced by two years. Beyond the particular case studied here, this analysis suggests that the right design of any solar + STES system should be led by the solar production. On the contrary, the traditional design intends to fulfill one demand (space heating) concentrated during winter, and so, its performance is noticeably penalized, and the solution is definitely not to put a larger tank. Unfortunately, up today the poor performance of these projects has shown that this solar technology is (by far) unaffordable. Maybe its best days have gone, considering the enormous improvements achieved by another solar technology (using photovoltaic panels + heat pump + small daily-storage water tank), as it was discussed here

Avances en la elaboración de un sistema termosolar automatizado de bajo costo que utiliza manguera de riego de PEBD

Se muestran los primeros avances obtenidos en la elaboración de un sistema automatizado de bajo costo para el calentamiento de agua por energía solar. El mismo consta básicamente de un absorbedor lineal formado por manguera de riego de polietileno de baja densidad (PEBD) y una cubierta transparente de botellas de PET. El agua en la manguera al llegar a cierta temperatura se descarga, en forma pulsada y automática, hacia un tanque térmico de almacenamiento. Esta acción es llevada a cabo por la apertura de una electroválvula comandada por un termostato bimetálico intercalado en la manguera. Esta automatización permite que el sistema trabaje en el rango de máxima eficiencia. Para conocer las propiedades térmicas del sistema de manguera-PET se caracterizaron los materiales constituyentes y se evaluó al sistema en distintas configuraciones. Se comprobó el funcionamiento de la automatización en dos prototipos realizados con manguera de PEBD de ¾”, uno cubierto por PET y otro cubierto con policarbonato alveolar. Se evaluó la producción de agua caliente en ambos. Estos trabajos apuntan a obtener un sistema automatizado de aprovechamiento de la energía solar simple, eficiente y económico que propicie el reciclaje y la autoconstrucción.Are shown first progress in developing a low-cost automated system for heating water by solar energy. Basically consists of an absorber composed of irrigation hose of low density polyethylene (LDPE) and a transparent cover of PET bottles. The water in the hose at a certain temperature is discharged, automatically in pulsed form, to a thermal storage tank. This action is performed by opening a solenoid valve commanded by a bimetallic thermostat inserted in the hose, automation allows the system to operate in the range of maximum efficiency. To know the thermal properties of PET-hose system, constituent materials were characterized, and the system was evaluated in different configurations. Was checked the automatic discharge operation to two prototypes made with ¾ " LDPE hose , one covered with PET bottles, another covered with polycarbonate honeycomb. In this work aim to obtain a simple, efficient and economical automated system for the production of hot water by solar energy, conducive to recycling and the self build.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Nuevo colector solar térmico de bajo costo de flujo forzado autónomo por panel fotovoltaico

The development of simple and inexpensive design of solar thermal collectors is presented. They are based on a long LDPE hose, that works by forced recirculation assisted by a pump which is powered by a little photovoltaic panel. The feasibility of this simple and autonomous thermoidraulic configuration was experimentally demonstrated. A prototype, of 50 liters with 50 meters of hose (3/4") and a 2 W pump which is operated by 3W 12 V panel, has been elaborated. The prototype has worked with an average efficiency of 37%, reaching the water, on a winter day with solar average irradiances of 700 W / m2, a maximum temperature of 48 °C.Se presenta el desarrollo de colectores solares térmicos de bajo costo y simple diseño, basados en una larga manguera de PEBD que operan por recirculación forzada asistida por mini bomba regulada y alimentada por panel fotovoltaico. Se demostró experimentalmente la factibilidad de esta configuración termohidráulica simple y autónoma. Un prototipo (50 litros y 50 metros manguera de ¾”, bomba de 2W y panel fotovoltaico de 3W en 12 voltios) obtuvo eficiencias promedio del 37%, calentando agua a 48°C en invierno en Salta con irradiancias de 700 W/m2.Tema 3: Energía solar, aplicaciones térmicas y químicas.Facultad de Arquitectura y Urbanism

Propuesta de material multicapa aislante de bajo costo e impacto ambiental

El objetivo de este trabajo es mostrar las ventajas térmicas, ambientales y económicas, de un nuevo material compuesto propuesto para aislación térmica en viviendas. Se propone un sobre muro exterior que intercala varias cámaras de aire y capas de aislantes de baja emisividad infrarroja. Se desarrolla un modelo de resistencias térmicas unidimensional para calcular la transferencia de calor multimodal involucrada (conducción, convección y radiación), la cual se resuelve mediante iteración numérica. Como ejemplo, empleando 5cm de EPS (telgopor) en multicapas de 1 cm y cámaras de aire de 2cm, se obtiene una resistencia térmica similar a una capa sólida de EPS de 10 cm, dando un coeficiente global de transmisión de 0,346 W/m²ºK. Se compara también la energía y los gases de efecto invernadero en la fabricación y el transporte del EPS, y se evalúan sus costos y aspectos constructivos.The aim of this work is to demonstrate the thermal, economical and environmental advantages of a new thermal insulation design to improve dwellings’ efficiency. An array consisting of several layers of air chambers separated by an insulation material of low infrared emissivity is proposed. The multimodal heat transfer (conduction, convection and radiation) is modeled by unidirectional thermal resistances, solving the coupled equations by numerical iteration. As an example, the calculations for an array with five layers of EPS of 1 cm thickness separated by 2cm-wide air chambers are developed. The result is a global thermal transmittance value of 0,346 W/m²ºK, which is similar to the one obtained by a solid EPS insulation of 10 cm thickness. The energy used and the greenhouse gases emitted in the manufacturing and transport of the materials are also studied, as well as the cost of the alternatives and the installation possibilities.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES