太阳能热水器安装倾角的优化

Optimizing the Tilt Angle of Domestic Solar Water Heaters

结合气候气象条件、各月热能供需关系,在全年各月无热水浪费的前提下,探讨以单位面积年采光量最大、太阳能热水器寿命期内经济效益最大、各月太阳能保证率波动率最小为优化目标的家用热水器安装倾角的优化方案.结果表明:除了太阳能资源极度匮乏的地区,单位面积的年采光量最大所对应的集热器倾角β_(opt.1)为当地地理纬度加减5°;寿命期内经济效益最大所对应的最佳倾角大于β_(opt.1);除了西藏和云南外,年太阳能保证率波动率最小所对应的倾角为90°;单位面积年采光量最大所对应的优化方案性价比最高,太阳能保证率波动率最小所对应的优化年太阳能保证率最高,但经济效益最差.研究还发现,从全年供热稳定的角度看,市场上流行的倾角为45°的真空管太阳能热水器适合于云南和西藏地区,但从经济效益角度来看,倾角为45°不是最佳倾角方案.

In this article,the parametric optimizing the tilt angle of domestic solar water heaters for maximizing the annual collectible radiation on unit area of collector and life cycle economic benefit and for minimizing annual fluctuation of solar fraction is made based on local climatic conditions,monthly heat demand of users and the constrain of no extra solar heat supply over a year.Results show that,for solar water heaters selected for maximizing the annual collectible radiation on unit area of collectors,the optimal tilt-angle of solar collectors,βopt,1,is about 5°from the site latitude over China except in the areas with poor solar resources,and for solar water heaters selected for maximizing its life cycle economic benefit,the optimal tilt-angle,is much higher than β_（opt,1）;whereas for those selected for minimizing fluctuation of solar fraction over a yea,except Tibet and Yunnan,the optimal tilt-angle is 90°.Results also indicate that,solar heaters selected for maximizing annual collectible radiation shares the highest ratio of life cycle economic benefit to investment,and the selection for minimizing fluctuation of solar fraction over a year shares the highest annual solar fraction but the least in life cycle economic benefit.It is also found that,from the point of stable solar heat supply over a year,the most common all-glass evacuated solar water heaters with a tilt-angle of 45° is suitable in Yunnan due to the climatic conditions over a year and Tibet due to the abundant solar resource,but not from the point of its life cycle economic benefit.