Erkki Hiltunen - Academia.edu (original) (raw)

Papers by Erkki Hiltunen

Energy Sources Part B-economics Planning and Policy, Jan 2, 2016

ABSTRACT Of the potential sources of renewables, the most promising one is microalgae, which are ... more ABSTRACT Of the potential sources of renewables, the most promising one is microalgae, which are viewed as a biofuel feedstock and technological solution for CO2 sequestration. Among microalgae-derived biofuels, biodiesel is one of the best application choices since microalgae have substantial amounts of oils. Nonetheless, microalgal biodiesel production is still in its infancy, since there is no commercial production on a large scale. The economic data and evaluation related to microalgal biodiesel production are incomplete and out of date, although lots of technological research has been carried out. This article demonstrates the pilot scale cultivation of microalgae in photobioreactors and evaluates the economics of producing oil from microalgae, including net energy ratio and cost-effectiveness evaluation. The contribution of this article lies in the presentation of an updated analysis of economic conditions for pilot scale microalgal oil production, which can provide the direction for future development of this important biofuel process.

Agronomy research, 2015

A renewable energy source called sediment energy is based on heat collection with tubes similar t... more A renewable energy source called sediment energy is based on heat collection with tubes similar to those used in ground energy and is installed inside a sediment layer under water body. In this paper, an investigation of temperature behaviour of heat carrier liquid is made during several years to evaluate utilization of sediment energy. This is done by evaluating temperature variations of heat carrier liquid and its correlation to air temperature. This increases advancement of knowledge how the temperature of the sediment recovers from the heat collection. The temperature variation of the liquid seems to correlate with the mean monthly air temperature. The selected methods clearly indicate that sediment energy seems to be yearly renewable because there is a clear correlation between air temperature and heat carrier liquid temperature.

SCIREA Journal of Geosciences

BioMed research international, 2016

In response to the energy crisis, global warming, and climate changes, microalgae have received a... more In response to the energy crisis, global warming, and climate changes, microalgae have received a great deal of attention as a biofuel feedstock. Due to a high lipid content in microalgal cells, microalgae present as a promising alternative source for the production of biodiesel. Environmental and culturing condition variations can alter lipid production as well as chemical compositions of microalgae. Therefore, application of the strategies to activate lipid accumulation opens the door for lipid overproduction in microalgae. Until now, many original studies regarding the approaches for enhanced microalgal lipid production have been reported in an effort to push forward the production of microalgal biodiesel. However, the current literature demonstrates fragmented information available regarding the strategies for lipid production improvement. From the systematic point of view, the review highlights the main approaches for microalgal lipid accumulation induction to expedite the appl...

2015 International Conference on Renewable Energy Research and Applications (ICRERA), 2015

Ground source heat has been utilized for a heating and cooling several decades in Finland. The bo... more Ground source heat has been utilized for a heating and cooling several decades in Finland. The bottom of a water body is also another heat source used but no so commonly in Finland. The asphalt and seabed sediment heat sources are quite new approaches. In this paper these four different heat energy sources are reviewed, analyzed and compared. All these heat sources are originating from solar radiation which makes them annually renewable. The evaluation data for the four heat sources have been collected during a one year period, 2014-2015. One year period is enough to see a short term behavior during the four seasons. The actual temperatures of topsoil ground, seabed sediment and subterranean layers beneath the asphalt are measured by distributed temperature sensing method. These three sources are located on the Vaasa Region, Finland in the radius of 5 km. Only the temperature data for the bottom of water body are obtained from the literature. All four sources provide promising temperatures. Sediment, ground and bottom of water body temperatures were quite stable but the seasonal variation can be noticed. Instead soil temperatures beneath the asphalt layer response the summer season rather strongly. That is why asphalt heat can be collected for storing in addition to direct usage for heating and cooling buildings.

Buildings are being demolished around year. This creates a lot of demolishing waste, which is the... more Buildings are being demolished around year. This creates a lot of demolishing waste, which is then processed further by companies specialized, for example, crushing concrete. This crushed waste includes concrete crush and several other materials. The problem is that a lot of this concrete crush as well as other demolishing waste ends up in landfills in many countries like Finland. It can be, however, recycled or reused: some usages of the concrete crush are already suggested and tested. In this paper, we study some aspect of usability of concrete crush for thermal heat storages. These thermal heat storages can be used with renewable and non-renewable heat sources. They are also identified as an important factor to reduce the greenhouse gas emissions: for example, renewable heat can be collected and stored in the summer, and used from the storage in the winter time. Since the natural storages like aquafers might be not available or they are protected, artificial storages need to be constructed and used. Thus, using concrete crush for heat storages would help in recycling the demolishing waste as well as combat climate change.

Science of The Total Environment

Climate change increase air, water and chlorophyll-a concentration in a few months. • Climate cha... more Climate change increase air, water and chlorophyll-a concentration in a few months. • Climate change effect is seen in air temperature influencing water temperature. • Water temperature and other parameters influenced chlorophyll-a concentration. • An indirect effect of air temperature on chlorophyll-a concentration is shown. • Understanding what kind of changes can be seen in water systems is important.

SWEDES Centre, 2019

Worldwide studies, including the Paris agreement, show that it is necessary to reduce dependency ... more Worldwide studies, including the Paris agreement, show that it is necessary to reduce dependency on the non-renewable energy sources and fossil fuels such as oil and coal. Transition to renewable energy is evident, and different reliable renewable energy systems are needed. The energy production with renewable energy sources is typically non-continuous when using only a single technique. This can be avoided by using a hybrid system and/or seasonal storage. This study introduces several hybrid systems and examples of storages operating mainly in Finland most of them in cooperation with University of Vaasa. Hybrid renewable energy systems (HRES) can be implemented in multiple different ways, scope varies from larger energy villages and other residential areas to single buildings. The amount of renewable energy generated by any HRES depends on both the technology and the meteorology. Some energy sources like different forms of geoenergy (geothermal energy) are available around the year. Instead, some renewable energy sources like solar and wind are often season dependent energy. To ensure constant production in HRES for the electric grid or the heating network, the energy storage or backup energy systems are in almost all cases needed. Advantages of the hybrid techniques are reliable, constant energy production and scalable energy production. When designing a hybrid system it also needs to be solved, what to do with the excess energy; whether to deliver it to the grid, use the dump loads or the storage systems.

Microalgae production in wastewaters is one of the best methods to reduce excessive nutrients. Me... more Microalgae production in wastewaters is one of the best methods to reduce excessive nutrients. Meanwhile, microalgae have also been considered as one of the most promising biofuel feedstock. Nonetheless, one of the major factors affecting algae technology application is growth performance in winter. In this present study, an integrated approach, which combined freshwater microalgae Chlorella zofingiensis cultivation in winter with artificial wastewater treatment, was investigated. Two treatments (pH regulation group and control group) were designed, and algal growth and nutrient removal were examined. In pH regulation group, acetic acid was used to regulate pH at between 6.8 and 7.2 three times per day. The results showed that the total nitrogen and total phosphate removal in pH regulation group could obviously increase from 45.2% to 73.5% and from 92.2% to 100%, respectively. The final biomass productivity of pH-regulated culture arrived at 66.94 mg L–1 day–1, which was around 3.6 ...

Biomass and Bioenergy, 2020

Abstract Flocculation is regarded as an effective, convenient and promising means for microalgal ... more Abstract Flocculation is regarded as an effective, convenient and promising means for microalgal harvesting of microalgal biomass. In this study three types of metal sulfates (aluminum sulfate, aluminum potassium sulfate and ferric sulfate) were applied as flocculants to harvest microalgae Chlorella vulgaris biomass. The optimal operating parameters such as dosage, rotation speed, flocculation time and sedimentation time during microalgal biomass harvesting were determined, and the effects of metal sulfate application as flocculants on lipid extraction were investigated. The results showed that the optimal dosage for the three flocculants to harvest microalgal biomass was identically 2.5 g L−1, and the optimal rotation speeds for coagulation and flocculation were 150 and 25 rpm, respectively, while the flocculation time of 10 min was found to be appropriate. The findings also suggested that metal residuals in flocculated biomass would affect lipid extraction, resulting in 5.9%, 4.4% and 3.3% reduction of lipid contents for aluminum sulfate, aluminum potassium sulfate and ferrous sulfate, respectively. The contribution of this study lies in the provision of the optimal operating parameters during the microalgal biomass flocculation, thus potentially offering the technical guidance for the harvesting of microalgal biomass using metal sulfates as flocculants in practice.

Renewable and Sustainable Energy Reviews, 2016

Microalgae as a renewable and alternative energy feedstock have come under increased research int... more Microalgae as a renewable and alternative energy feedstock have come under increased research interest, in response to the energy crisis, global warming and climate changes. Microalgal growth needs large amounts of chemical or organic fertilizers, causing substantial costs and risking the environment due to nutrient release. Using nutrient-rich wastewaters to cultivate microalgae appears a promising choice for the removal of nutrients and production of biofuels. Meanwhile, livestock production is rapidly increasing, especially in developing countries, because of increased consumption demands for meat. As a result, large quantities of animal wastes are left over, threatening environmental hygiene and becoming a barrier for development if not disposed of appropriately. Hence, the efforts to seek for an effective way to manage livestock wastes are also extremely important. This paper evaluates the feasibility of microalgal cultivation with livestock waste compost for continuous production of multiple bioproducts such as high values, biodiesel and biogas. A feasibility framework is proposed to fulfill this target. System integration and engineering is highlighted and main challenges are also discussed. Through careful microalgal biorefinery, the improvement of the economics of microalgal biofuels can be potentially achieved. Applying livestock waste compost to cultivate microalgae appears as a sustainable solution to realize both livestock waste management and bioproducts recovery, thus driving the industry towards sustainable growth.

Rapidly Quenched Metals, 1985

EDXD and Mossbauer spectroscopy have been applied to study the primary crystallization of α-Fe du... more EDXD and Mossbauer spectroscopy have been applied to study the primary crystallization of α-Fe during the isothermal heat treatment of a Fe-B metallic glass. The results are compared and the possible sources of systematic errors are discussed. The crystallization of α-Fe changes from a parabolic growth to a linear growth. Further development of the methods can lead to unique possibilities to study the crystallization kinetics of each phase simultaneously during more complicated processes.

Energies, 2022

Suvilahti, a suburb of the city of Vaasa in western Finland, was the first area to use seabed sed... more Suvilahti, a suburb of the city of Vaasa in western Finland, was the first area to use seabed sediment heat as the main source of heating for a high number of houses. Moreover, in the same area, a unique land uplift effect is ongoing. The aim of this paper is to solve the challenges and find opportunities caused by global warming by utilizing seabed sediment energy as a renewable heat source. Measurement data of water and air temperature were analyzed, and correlations were established for the sediment temperature data using Statistical Analysis System (SAS) Enterprise Guide 7.1. software. The analysis and provisional forecast based on the autoregression integrated moving average (ARIMA) model revealed that air and water temperatures show incremental increases through time, and that sediment temperature has positive correlations with water temperature with a 2-month lag. Therefore, sediment heat energy is also expected to increase in the future. Factor analysis validations show that...

Ground Source Heat Hump is one of the emerging technic to utilize the reservoir of geothermal ene... more Ground Source Heat Hump is one of the emerging technic to utilize the reservoir of geothermal energy in Europe. The crucial factor is to find the optimal length of the borehole to successfully design a heating system. The length of the borehole varies depending on the geographical area, the capacity of the heat pump and heat load of the desired building in consideration. Several methods have been theorized and validated using the experimental measurements to find the optimal length of the borehole. The most commonly used methods are American Society of Heating, Refrigeration and Air-conditioning Engineers and International Ground Source Heat Pump Association for sizing borehole heat exchanger. In this paper, an existing system is analyzed, for a 60 kilo Watts heat pump in an area of Finland with a ground source 250 meters of Borehole Heat Exchanger. Coefficient of Performance for current scenario is calculated, an optimal length is found for the heat capacity of the heat pump to enh...