| 1. |
- Börjesson, Pål, et al.
(författare)
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Biomass Transportation
- 1996
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 9:1-4, s. 1033-1036, s. 1033-1036
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Tidskriftsartikel (refereegranskat)abstract
- Extensive utilisation of logging residues, straw, and energy crops will lead to short transportation distances and thus low transportation costs. The average distance of transportation of biomass to a large-scale conversion plant, suitable for electricity or methanol production using 300 000 dry tonne biomass yearly, will be about 30 km in Sweden, if the conversion plant is located at the centre of the biomass production area. The estimated Swedish biomass potential of 430 PJ/yr is based on production conditions around 2015, assuming that 30% of the available arable land is used for energy crop production. With present production conditions, resulting in a biomass potential of 220 PJ/yr, the transportation distance is about 42 km. The cost of transporting biomass 30-42 km will be equivalent to 20-25% of the total biomass cost. The total energy efficiency of biomass production and transportation will be 95-97%, where the energy losses from transportation are about 20%. Biomass transportation will contribute less than 10% to the total NOx, CO, and HC emissions from biomass production, transportation, and conversion.
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| 2. |
- Gehlin, S E A, et al.
(författare)
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Influence on thermal response test by groundwater flow in vertical fractures in hard rock
- 2003
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Ingår i: Renewable Energy. - 0960-1481 .- 1879-0682. ; 28:14, s. 2221-2238
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Tidskriftsartikel (refereegranskat)abstract
- In this paper different approaches to groundwater flow and its effect in the vicinity of a borehole ground heat exchanger are discussed. The common assumption that groundwater flow in hard rock may be modelled as a homogeneous flow in a medium with an effective porosity is confronted and models for heat transfer due to groundwater flow in fractures and fracture zones are presented especially from a thermal response test point of view. The results indicate that groundwater flow in fractures even at relatively low specific flow rates may cause significantly enhanced heat transfer, although a continuum approach with the same basic assumptions would suggest otherwise. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 3. |
- Gehlin, S E A, et al.
(författare)
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The influence of the thermosiphon effect on the thermal response test
- 2003
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Ingår i: Renewable Energy. - 0960-1481 .- 1879-0682. ; 28:14, s. 2239-2254
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Tidskriftsartikel (refereegranskat)abstract
- The issue of natural and forced groundwater movements, and its effect on the performance of ground heat exchangers is of great importance for the design and sizing of borehole thermal energy systems (BTESs). In Scandinavia groundwater filled boreholes in hard rock are commonly used. In such boreholes one or more intersecting fractures provide a path for groundwater flow between the borehole and the surrounding rock. An enhanced heat transport then occurs due to the induced convective water flow, driven by the volumetric expansion of heated water. Warm groundwater leaves through fractures in the upper part of the borehole while groundwater of ambient temperature enters the borehole through fractures at larger depths. This temperature driven flow is referred to as thermosiphon, and may cause considerable increase in the heat transport from groundwater filled boreholes. The thermosiphon effect is connected to thermal response tests, where the effective ground thermal conductivity is enhanced by this convective transport. Strong thermosiphon effects have frequently been observed in field measurements. The character of this effect is similar to that of artesian flow through boreholes. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 4. |
- Gustavsson, Leif, et al.
(författare)
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Biomass Utilisation and Transportation Demands
- 1996
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 9:1-4, s. 1037-1040
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Tidskriftsartikel (refereegranskat)abstract
- The need for biomass transportation depends on the balance between locally produced biomass and the local demand for fuel. In Sweden, more than 80% of the biomass assumed to be required to replace fossil fuels for the production of electricity and heat can be produced locally within each county, if biomass is extensively utilised. The average transportation distance of the remaining 20% will be between 100 and 200 km, which increases the cost of this biomass by 15–20%. Considering a yearly biomass potential of 430 PJ, based on estimated biomass production conditions around 2015, 190 PJ/yr excess biomass will remain after fossil fuels for electricity and heat production have been replaced. This biomass can be converted to methanol to replace petrol and diesel, or can be used in new electricity production plants. The production of biomass-based methanol will not lead to a high demand for transportation, as the methanol produced from local biomass and can mainly be used locally. Biomass used for electricity production will increase the need for transportation if electricity is cogenerated in district heating systems, as such systems are usually located in densely populated areas with a deficit of biomass.
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| 5. |
- Hellström, Bengt, et al.
(författare)
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The impact of optical and thermal properties on the performance of flat plate solar collectors
- 2003
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Ingår i: Renewable Energy. - 0960-1481. ; 28:3, s. 331-344
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Tidskriftsartikel (refereegranskat)abstract
- The impact of the optical properties on the annual performance of flat plate collectors in a Swedish climate has been estimated with the MINSUN program. The collector parameters were determined with a theoretically based calculation program verified from laboratory measurements. The importance of changes in solar absorptance and thermal emittance of the absorber, the addition of a teflon film or a teflon honeycomb, antireflection treatment of the, cover glazing and combinations of these improvements were investigated. The results show that several improvements can be achieved for solar thermal absorbers. A combined increase in absorptance from 0.95 to 0.97 and a decrease in emittance from 0.10 to 0.05 increase the annual performance with 6.7% at 50 degreesC operating temperature. The increase in performance by installing a teflon film as second glazing was estimated to 5.6% at 50 degreesC. If instead a teflon honeycomb is installed, a twice as high performance increase is obtained, 12.1 %. Antireflection treatment of the cover glazing increases the annual output with 6.5% at 50 degreesC. A combination of absorber improvements together with a teflon honeycomb and an antireflection treated glazing results in a total increase of 24.6% at 50 degreesC. Including external booster reflectors increases the expected annual output at 50 degreesC to 19.9-29.4% depending on reflector material. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 6. |
- Langniss, Ole
(författare)
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Instruments to foster renewable energy investments in Europe
- 1996
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481. ; 9:1-4, s. 1112-1115
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Tidskriftsartikel (refereegranskat)abstract
- Since capital needs are high when investing in Renewable Energy Technologies (RET), well adapted financial schemes are essential, including well fitted financial support. Supporting the dissemination of RET means supporting people, not technologies. Though, support mechanism have to be adapted to people not to technologies. A recent study for the European Parliament compares support mechanisms for RET in several European countries by describing case studies. Six different investor types can be identified, each one standing for a specific amalgam of motivation, energy needs, financial possibilities and risk-averse. Each of these types has its specific importance for different RET and different stages of RET's market penetration. Also the size of the market for RET, represented by each investor type, is different.
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| 7. |
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| 8. |
- Granqvist, C. G., et al.
(författare)
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Progress in Smart Windows Research: Improved Electrochromic W Oxide Films and Transparent Ti-Ce Oxide Counter Electrodes
- 1996
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Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 8:1-4, s. 97-106
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Tidskriftsartikel (refereegranskat)abstract
- We review recent work on sputter deposited W-oxide-based films. Improved electrochemical durability was obtained by electron bombardment during deposition, and enhanced coloration/bleaching dynamics was obtained by fluorination. Spectrally resolved scattering measurements indicated that haze levels ≪ 1 % could be reached. Oblique angle deposition could yield angular selectivity. New results are given for sputtered Ti-Ce oxide films, showing their capacity as counter electrodes in transparent electrochromic devices.
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| 9. |
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| 10. |
- Abedi, Hamidreza, 1979
(författare)
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Assessment of flow characteristics over complex terrain covered by the heterogeneous forest at slightly varying mean flow directions: (A case study of a Swedish wind farm)
- 2023
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Ingår i: Renewable Energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 202, s. 537-553
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Tidskriftsartikel (refereegranskat)abstract
- The impact of heterogeneous forest canopies and complex terrain on the horizontal distortion of the inflow is studied. Large-Eddy Simulation (LES) of the neutral Atmospheric Boundary Layer (ABL) flow is performed for a wind farm in Sweden for three cases associated with three different wind directions at the range of the static yaw misalignment (≃±6∘) where the yaw control system is not activated. The ground topography and forest properties for the numerical modeling are extracted from the Airborne Laser Scanning (ALS) 3D data. The wind turbines within the wind farm are introduced using the actuator disk model. To focus on the airflow deflection only by the complex terrain and vegetation, the study is limited to upstream wind turbines without any wake interaction. The predicted mean wind speed and turbulence intensity for the upstream wind turbines are compared against the nacelle-mounted anemometers taken from the wind farm's turbine SCADA data. To quantify the additional load and moments induced at the rotor blades by the horizontal misalignment of the incoming flow, aero-structural simulation of the upstream wind turbines in the wind farm for all three cases is performed. The results show that the horizontal distortion of the inflow over the rotor swept area is usually kept below the range of static yaw misalignment (≃6∘) for the majority of the upstream wind turbines for all three cases. However, the impact of a large vertical shear exponent leading to misinterpretation of the results must be taken into consideration. Furthermore, the load imbalance of the rotor due to the vertical wind shear has the least direct contribution to the yaw moment. However, for a mean vertical shear exponent larger than α=0.25, contrary to expectation, a positive mean yaw moment under the positive-yawed inflow may be observed.
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