The two main justifications for punishment, and the ones most relevant for pecuniary sanctions are retribution and deterrence. This chapter aim to theoretically assess day fines in light of these two justifications. Whereas day fines seem to fit well the deterrence goal, their legitimacy in light of the proportionality principle (mostly attributed to retribution) is less straight forward. A fine, which accounts not only for the severity of the offence, but also for the income of the offender, has a better potential to deter all criminals irrespective of their income. On the other hand, such fine might not seem to be proportional to the severity of the crime if also income is accounted for, thus not fulfilling the retribution goal. However, if looking more broadly on the principle of proportionality, one can see day fines are more proportional than fixed fines. The number of days is the element which needs to be proportionate to the severity of the offence. The daily unit, on the other hand, assures that the imposed punitive bite of the sanction is similar for all offenders irrespective of their income. In addition to this analysis, this chapter discusses the theoretically optimal model of day fines.

Chapter 4 extends the aerodynamic discussions of the preceding chapter to show how the rotor net loads (power, thrust, and torque) are developed. The dimensionless power coefficient (Cp) curve is introduced, and the relationship between rotor tip speed ratio and optimum solidity is explained. The variation of thrust loading with wind speed on an ideal pitch-controlled rotor is explained from simple theory and illustrated with measurements from a full-scale wind turbine. Equations governing the chord and twist distributions for an optimised blade are given and discussed in the context of some historic blade types, with illustrations. Rotor aerodynamic control is explained with reference to fixed-pitch stall regulation and variable blade pitch in both positive and negative senses. The influence of blade number is examined, with discussion of the advantages and disadvantages of one-, two-, and three-bladed wind turbines. The chapter concludes with a brief overview of alternative aerodynamic control devices, including tip vanes and ailerons, and the downwind rotor configuration (with examples).