Age-related efficiency loss of household refrigeration appliances: Development of an approach to measure the degradation of insulation properties

Despite the omnipresence of household refrigeration appliances, there is still a lack of knowledge about their age-related efficiency loss over time. Past studies provide basic evidence for increasing electricity consumption of cooling appliances with ageing but fail to investigate the associated technical wear. Concentrating on the degradation of the thermal insulation, we first determined the ageing process of sealed samples of polyurethane rigid foam by investigating changes in cell gas composition and thermal conductivity over time. Simultaneously, the main challenge was to develop an approach that investigates the age-related efficiency loss of the insulation without its destruction. This testing procedure is referred to as the Bonn method. The non-destructive Bonn method was applied to varying refrigerator models in a series of successive experiments to evaluate the insulation degradation over time. Subsequently, the physical relationship between the test value of the Bonn method and the heat transfer through the multi-layered compartment walls of domestic refrigeration appliances was established, ultimately characterising the degrading insulation in terms of increasing heat transfer. Our results give substantiated evidence that the efficiency loss of cooling appliances is greatly influenced by insulation degradation over time. The ageing of sealed samples of polyurethane rigid foam indicates a large initial increase of thermal conductivity by 15% within the first year, corresponding to a change in cell gas composition. These results are in line with those of the Bonn method, emphasising an increasing heat flow through the multi-layered compartment walls of domestic refrigerators with ageing. Therewith, the present study is of significance to a wide range of stakeholders and forms the basis for future research.BMWi, 03ET1544, ALGE: Alterungsmechanismen von Haushaltskältegeräte

Determining the heat flow through the cabinet walls of household refrigerating appliances

The increase of the thermal conductivity of PUR foam in the insulation of the cabinet is an important cause for aging processes of household refrigerating appliances. To determine the influence of the PUR foam aging on energy consumption, the development of a new measurement method is necessary because current methods influence the aging behavior of household refrigerators and are therefore not applicable in general. Based on a latent heat sink, constructed as an ice water bucket, a new measurement method is developed to determine the k · A value over time. With this method, the k · A value of four household refrigerating appliances was determined over an interval of 14 months. The k · A value increased between 3.6 % and 11.5 % during this period.BMWi, 03ET1544A, Verbundvorhaben ALGE: Alterungsmechanismen von Haushaltskältegeräte

Preventing Falls in Physically Active Community-Dwelling Older People: A Comparison of Two Intervention Techniques

Background: Falls are common in physically active older people; however, most intervention studies have been targeted at frail older people. Objective: To evaluate the effectiveness of two intervention techniques for preventing falls in physically active community-dwelling older people. Methods: Two hundred and seventeen people (120 men and 97 women) aged between 70 and 90 years recruited from a health insurance company membership database were randomly allocated to receive either a psychomotor intervention focusing on body awareness, body experience and coordination, a fitness intervention focusing on functional skills, strength, endurance and flexibility, or no intervention (control group). The outcome measures were prospective falls (number of fallers, number of multiple fallers, number of falls and falls rate) and measures of physical performance (Timed Up and Go Test, maximal step length, sit-to-stand time, normal and fast walking speed). Results: At the 4- month follow-up, significant improvements in the Timed Up and Go Test and sit-to-stand times were observed for both the psychomotor and fitness intervention groups. During the 12-month follow-up period, 39% of the participants fell at least once, and 19% fell on multiple occasions. The pro- portion of fallers in the fitness intervention group was 23% less than in the control group (RR = 0.77, 95% CI 0.60–0.97), but no significant reduction in falls was observed in the psychomotor intervention group. Conclusion: A fitness training program improves some aspects of physical performance and reduces falls by 23% in physically active older people

Investigating the real life energy consumption of refrigeration appliances in Germany: Are present policies sufficient?

Domestic refrigeration appliances are standard household commodities. Although policies, such as the energy labelling, prompted technical improvements and decreased appliance energy consumption throughout recent decades, important parameters were disregarded. These refer to the efficiency loss over time and the consumer behaviour. The objective of this contribution was to develop a dynamic energy model to determine the power consumption of refrigeration appliances considering degradation factors and behaviour. These were included by model parameters for direct consumer interactions, such as the storage behaviour, door openings and temperature setting, as well as indirect actions, e.g. exposing an appliance to specific temperature conditions at an installation site. For this, an online-survey was conducted to evaluate the consumer behaviour. A total of 706 consumers participated in the national questionnaire, serving as input for the dynamic energy model. It was found that the efficiency loss increases the power consumption by at least 1% annually, leading to an excess of 10% after 10 years of usage. Another important finding was that 32.5% of appliance's power consumption results from consumer behaviour, whereas the promotion of behavioural changes leads to a significant decrease of the consumer-induced consumption. Consequently, this study provides a tool to evaluate the impact of policies targeting refrigeration appliances, stressing that efficiency loss and behaviour should be integrated into future policy approaches.BMWi, 03ET1544A, Verbundvorhaben ALGE: Alterungsmechanismen von Haushaltskältegeräten - Teilprojekt: Bestimmung des Degenerationsverhaltens und Konstruktion der Gerät