title: Integration of solar heating into heat recovery loops using constant and variable temperature storage

authors: Walmsley, Michael R.W.

subjects: SELECTION

abstract: Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable.

text: Integration of solar heating into heat recovery loops using constant and variable temperature storage Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable.

year: 2013-01-01

title: Using quotitive division problems to promote place-value understanding

authors: Bicknell, Brenda

abstract: Using quotitive division problems to promote A robust understanding of place value is essential. Using a problem-based approach set within meaningful contexts, students' attention may be drawn to the multiplicative structure of place value. By using quotitive division problems through a concrete-representational-abstract lesson structure, this study showed a powerful strengthening of Year 3 students' conceptual understanding of place value.

text: Using quotitive division problems to promote place-value understanding Using quotitive division problems to promote A robust understanding of place value is essential. Using a problem-based approach set within meaningful contexts, students' attention may be drawn to the multiplicative structure of place value. By using quotitive division problems through a concrete-representational-abstract lesson structure, this study showed a powerful strengthening of Year 3 students' conceptual understanding of place value.

year: 2017

title: Ohaaki: A power station on Maori land

authors: Stokes, Evelyn

subjects: Ohaaki Geothermal Power Station

abstract: This paper is about a geothermal power station called Ohaaki, constructed over the period 1982-1989 on Maori land close by Te Ohaaki Marae and the ancestral papakainga of Ngati Tahu. This is a personal account of the impact of this project on Ngati Tahu rather than a history of the construction of the power station.

text: Ohaaki: A power station on Maori land This paper is about a geothermal power station called Ohaaki, constructed over the period 1982-1989 on Maori land close by Te Ohaaki Marae and the ancestral papakainga of Ngati Tahu. This is a personal account of the impact of this project on Ngati Tahu rather than a history of the construction of the power station.

year: 2003