Note 13. Commitments and Contingencies (a) Operating Leases We lease various facilities and equipment under noncancelable operating leases with terms ranging from 12 months to 120 months. Scheduled rent increases are recorded on a straight-line basis over the entire term of the lease. Rental expense charged under all operating leases (including leases with terms of less than one year) was $25.5 million, $19.3 million and $11.5 million for the years ended December 31, 2018, 2017 and 2016, respectively. Future minimum lease payments under noncancelable operating leases with terms of one year or more as of December 31, 2018 are as follows (in thousands): 2019 $ 28,173 2020 26,871 2021 22,942 2022 22,065 2023 21,583 Thereafter 61,049 Total future minimum lease payments $ 182,683 (b) Common Stock Warrants In connection with the note purchase agreement dated December 29, 2014, for the purchase of $10.0 million of subordinated convertible promissory notes, a minimum of 160,424 warrants were issued to purchase common stock with an exercise price equal to the lesser of $24.30 or 85% of the IPO price of $11.00 per share, accordingly, after the IPO, the exercise price was $9.35. The warrants were immediately exercisable and expired no later than eight years from the date of issuance. The unamortized fair value of the warrants was expensed upon conversion of the convertible promissory notes concurrent with the IPO. These warrants were all exercised during 2018. (c) Legal Proceedings From time to time, we may be involved in disputes or litigation relating to claims arising out of its operations. In March 2015, a complaint was filed against us in the Superior Court of the State of Arizona (Maricopa County) by a former employee, alleging that we had agreed to compensate the employee upon any future sale of the Company. We filed a motion to dismiss the complaint in April 2015, which was denied. We subsequently filed an answer to the complaint in July 2015 denying the substantive allegations of the complaint. The parties completed court-ordered mediation in December 2015 but were not able to reach a settlement. We filed a motion for summary judgment to dismiss the complaint in April 2016 and the court denied the motion in August 2016. The court has set a trial date for June 2019. We continue to deny the substantive allegations of the complaint and intend to vigorously defend this lawsuit; however, we are currently unable to determine the ultimate outcome of this case. In August 2015, we entered into a transition agreement with our former Senior Vice President  Asia, pursuant to which that individual transitioned out of this role at the end of 2015 and was to serve in a consulting capacity in 2016 and 2017. In January 2016, following our discovery that the individual had materially violated the terms of the transition agreement, we terminated the consultancy for cause. In April 2016, an arbitration claim was filed in China by the individual with the Taicang Labor and Personnel Dispute Arbitration Committee alleging that we improperly terminated the transition agreement. The individual is demanding that we honor the terms of the transition agreement and pay compensation and fees under the transition agreement, which in the aggregate totals approximately $2.6 million. In addition, the individual is also challenging the validity of our termination of an option to purchase 164,880 shares of our common stock and 77,760 restricted stock units awarded under the 2015 Plan, which were canceled in January 2016 when the consultancy was terminated. The Taicang Labor and Personnel Dispute Arbitration Committee awarded damages to the individual of approximately $1.2 million but rejected the claims regarding the termination of the stock option and restricted stock unit awards. We subsequently appealed the arbitration award in favor of the individual to the Taicang Municipal Peoples Court, which affirmed the arbitration award in June 2018. We appealed this judgment to an appellate level court in the Jiangsu Province and the appellate court affirmed the judgment of the Taicang Municipal Peoples court and we paid the judgement award in the fourth quarter of 2018. We currently are evaluating whether to further appeal this matter. In June 2018, Iowa OSHA, a division of the Iowa Department of Labor, issued a citation and notification of penalty to us alleging that certain of our workplace practices and conditions at our Newton, Iowa wind blade manufacturing facility had violated the Iowa Occupational Safety and Health Act. Specifically, the citation cited us for multiple alleged violations and proposed that we pay an aggregate penalty of $0.2 million. In June 2018, we notified Iowa OSHA that we were contesting all of the alleged violations and proposed penalties. In June 2018, the Labor Commissioner of the Iowa Department of Labor subsequently filed a complaint with the State of Iowa Employment Appeal Board, petitioning the appeal board to affirm the citation and notification of penalty that Iowa OSHA issued to us. In July 2018, we then filed a response with the appeal board denying the substantive allegations of the complaint. A hearing date has been set for June 2019 and the matter remains pending. From time to time, we are party to various lawsuits, claims, and other legal proceedings that arise in the ordinary course of business, some of which are covered by insurance. Upon resolution of any pending legal matters, we may incur charges in excess of presently established reserves. Our management does not believe that any such charges would, individually or in the aggregate, have a material adverse effect on our financial condition, results of operations or cash flows. (d) Insurance/Self-Insurance We use a combination of insurance and self-insurance for a number of risks, including claims related to our employee health care, workers compensation and general liability. Liabilities associated with these risks are estimated based on, among other things, historical claims experience, severity factors, and other actuarial assumptions. Our loss exposure related to self-insurance is limited by stop loss coverage on a per occurrence and aggregate basis. We regularly analyze our reserves for incurred but not reported claims, and for reported but not paid claims related to our self-funded insurance programs. While we believe our reserves are adequate, significant judgment is involved in assessing these reserves such as assessing historical paid claims, average lags between the claims incurred date, reported dates and paid dates, and the frequency and severity of claims. There may be differences between actual settlement amounts and recorded reserves and any resulting adjustments are included in expense once a probable amount is known. (e) Dividend Restrictions Certain of our subsidiaries are limited in their ability to declare dividends without first meeting statutory restrictions of the Peoples Republic of China, including retained earnings as determined under Chinese-statutory accounting requirements. Until 50% ($21.6 million) of registered capital is contributed to a surplus reserve, our Chinese operations can only pay dividends equal to 90% of after-tax profits (10% must be contributed to the surplus reserve). Once the surplus reserve fund requirement is met, we can pay dividends equal to 100% of after-tax profit assuming other conditions are met. At December 31, 2018, the amount of the surplus reserve fund was $6.5 million. (f) Collective Bargaining Agreements In 2016, we entered into a three-year collective bargaining agreement with certain of our employees at our first Turkey facility. The agreement resulted in an average increase in pay of approximately 20% for employees covered by the agreement. In addition, beginning in July 2017, this collective bargaining arrangement also covered similarly situated employees at our second Turkey facility. In March 2018, we entered into a collective bargaining agreement with a labor union for certain of our employees at the Matamoros, Mexico facility. Currently, there are no other employees covered by collective bargaining agreements. We believe that our relations with employees are good, and there have been no major work stoppages in recent years.